You might have a task to use or download one or all files attached to document saved via CV01N transaction. This is not a big deal really, you just need to use some FMs available in standard of SAP like  'CVAPI_DOC_GETDETAIL''CVAPI_DOC_CHECKOUTVIEW' or  SCMS_DOC_READ'.  These FMs allows you the check the details of document, check it and then read its content. Of course sometimes you'll have to zip the files before the downloading and here in my code I used method "zip" for which code you can find here.  While reading the code you may also find another Z-method called "get_filename_from_path", its code is posted here. The method I'm posting bellow allows you to choose if during download of files from document you want to zip them all together into one zip file or if you want to zip them separatelly. In table ET_FILES you'll find all files that were attached to document, field "UPDATEFLAG" will be set to 'D' if file was succesfully downloaded to PC. If you don't want to download the file but you want to get it for futher use you'll have to request ET_XSTRING table. In other case do not request this parameter as it is a sign for method that you don't want to donwload the files.

Types:

TT_RA_FILENAME type range of CVAPI_DOC_FILE-FILENAME.
TT_XSTRING type table of xstring.

Importing:

I_DOKAR TYPE DRAW-DOKAR ->Document Type
I_DOKNR TYPE DRAW-DOKNR ->Document number
I_DOKTL TYPE DRAW-DOKTL   ->Document Part
I_DOKVR TYPE DRAW-DOKVR  ->Document Version
I_DOWNLOAD_DIRECTORY TYPE STRING -> path to download the fiels
I_ZIP_FILES TYPE C OPTIONAL -> mark it 'X' if you want to zip the files before downloading
I_ZIP_SEPARATELY TYPE C OPTIONAL -> mark it 'X' if you want to zip each file found in document separately
I_NAME_FILTER TYPE TT_RA_FILENAME OPTIONAL -> Range for filter filenames - select which documents you want to download
I_FILENAME TYPE CSEQUENCE OPTIONAL -> filename for zip - used if you zip all files into zip container

Exporting:

ET_FILES TYPE CVAPI_TBL_DOC_FILES -> Table with all files found in document 
ET_XSTRING TYPE TT_XSTRING -> TT_XSTRING -> Table of xstrings (each file in separated line)

Exceptions:

ZIP_ERROR -> Error while zipping
DOCUMENT_ERROR -> Error while reading document

Implementation:

method save_document_on_pc.
  datam_exists type abap_bool.
  datam_temp_dir(255type c.
  datamt_drat type table of drat.
  datams_drat type drat.
  datamt_files type table of cvapi_doc_file.
  datamt_components type table of cvapi_doc_comp.
  datams_draw type draw.
  datam_mimetype type mimetypes-type.
  datamt_files_checkout type table of cvapi_doc_file.
  datams_files_checkout type cvapi_doc_file.
  datamt_content type table of drao.
  datams_content type drao.
  datams_message type messages.
  datam_fail type c.
  datam_size type i.
  datams_bindata type xstring.
  datams_zipdata type xstring.
  datam_filename type string.
  datam_filenamefull type string.
  datam_extension type string.
  datamo_zipper type ref to cl_abap_zip.
  datamt_accessinf type standard table of scms_acinf.
  datams_accessinf type scms_acinf.
  datamr_name_filter type tt_ra_filename.
  field-symbols <filter> like line of mr_name_filter.
  datam_fileupper type string.

  mr_name_filter[] i_name_filter[].
  loop at mr_name_filter assigning <filter>.
    translate <filter>-low to upper case.
    translate <filter>-high to upper case.
  endloop.

  typesbegin of t_binline,
    line type drao-orblk,
  end of t_binline.

  datamt_bintab type standard table of sdokcntbin.
  datams_bintab type sdokcntbin.

  field-symbols<files> type cvapi_doc_file.

  create object mo_zipper.

  ms_draw-dokar i_dokar.
  ms_draw-doknr i_doknr.
  ms_draw-doktl i_doktl.
  ms_draw-dokvr i_dokvr.

  call function 'CVAPI_DOC_GETDETAIL'
    exporting
      pf_dokar     ms_draw-dokar
      pf_doknr     
ms_draw-doknr
      pf_dokvr     
ms_draw-dokvr
      pf_doktl     
ms_draw-doktl
      pf_read_drat 
abap_true
      pf_read_comp 
abap_true
    
importing
      psx_draw     ms_draw
    
tables
      pt_drat      mt_drat
      pt_files     
mt_files
      pt_comp      
mt_components
    
exceptions
      not_found    1
      no_auth      2
      error        3
      others       4.
  if sy-subrc ne 0.
    raise document_error.
  else.
    loop at mt_files assigning <files>.

      m_fileupper <files>-filename.
      translate m_fileupper to upper case.
      if m_fileupper not in mr_name_filter.
        append <files> to et_files.
        continue.
      endif.

      clear mt_files_checkout.
      clear mt_content.
      ms_files_checkout-description <files>-description.
      ms_files_checkout-lo_objid <files>-lo_objid.
      ms_files_checkout-ph_objid <files>-ph_objid.

      append ms_files_checkout to mt_files_checkout.

      call function 'CVAPI_DOC_CHECKOUTVIEW'
        exporting
          pf_dokar           ms_draw-dokar
          pf_doknr           
ms_draw-doknr
          pf_dokvr           
ms_draw-dokvr
          pf_doktl           
ms_draw-doktl
*          pf_content_provide = 'TBL'
        importing
          psx_message        ms_message
          psx_draw           
ms_draw
        
tables
          pt_files           mt_files_checkout
*          ptx_content        = mt_content
.

      if ms_message-msg_type ca 'EA'.
        m_fail abap_true.
        <files>-updateflag 'E'"error
        append <files> to et_files.
        continue.
      else.
        clear mt_bintab.
        clear ms_bindata.
        refreshmt_bintabmt_accessinf.

        call function 'SCMS_DOC_READ'
          exporting
            stor_cat              <files>-storage_cat
            doc_id                
<files>-ph_objid
          
tables
            access_info           mt_accessinf
            content_bin           
mt_bintab
          
exceptions
            bad_storage_type      1
            bad_request           2
            unauthorized          3
            comp_not_found        4
            not_found             5
            forbidden             6
            conflict              7
            internal_server_error 8
            error_http            9
            error_signature       10
            error_config          11
            error_format          12
            error_parameter       13
            error                 14
            others                15.
        if sy-subrc eq 0.
          read table   mt_accessinf into ms_accessinf index 1.
          m_size ms_accessinf-comp_size.
          if sy-subrc eq 0.
            z_my_special_class=>get_filename_from_path(
              exporting
                i_path         <files>-filename
              
importing
                e_filename     =  m_filename
                e_filenamefull 
=  m_filenamefull
                e_extension    
m_extension
                   
).

            if i_zip_files is not initial or et_xstring is requested.
              call function 'SCMS_BINARY_TO_XSTRING'
                exporting
                  input_length ms_accessinf-comp_size
                
importing
                  buffer       ms_bindata
                
tables
                  binary_tab   mt_bintab
                
exceptions
                  failed       1
                  others       2.
              if sy-subrc eq 0.

                    if et_xstring is requested.
                      append ms_bindata to et_xstring.
                      <files>-updateflag 'D'.
                      append <files> to et_files.
                      continue.
                    endif.
                "just for zipping
                if i_zip_separately is not initial.
                  z_my_special_class=>zip(
                    exporting
                      i_xstring           ms_bindata
*                i_string            = i_string
                      i_filename          m_filenamefull
*                i_solix             = i_solix
*                i_soli              = i_soli
                      i_get_xstring       'X'
                    importing
                      e_xstring           ms_zipdata
                    
exceptions
                      attachment_is_empty 1
                      string_conv_error   2
                      others              3
                         ).
                  if sy-subrc <> 0.
                    raise zip_error.
                  endif.
                else.
                  z_my_special_class=>zip(
                  exporting
                    i_xstring           ms_bindata
*                i_string            = i_string
                    i_filename          m_filenamefull
*                i_solix             = i_solix
*                i_soli              = i_soli
                    i_get_xstring       space
                  
changing
                    c_zipper            mo_zipper
*              importing
*                e_xstring           = ms_zipdata
                  exceptions
                    attachment_is_empty 1
                    string_conv_error   2
                    others              3
                    ).
                  if sy-subrc <> 0.
                    raise zip_error.
                  endif.
                endif.

                if i_zip_separately is not initial.
                  ms_bindata ms_zipdata.
                  m_extension 'zip'.
                  refresh mt_bintab[].
*   Convert the XSTRING to Binary table
                  call function 'SCMS_XSTRING_TO_BINARY'
                    exporting
                      buffer     ms_bindata
                    
tables
                      binary_tab mt_bintab.
                endif.
              endif.
            endif.

            if i_zip_separately is not initial or i_zip_files is initial.

              clear m_exists.
              cl_gui_frontend_services=>directory_exist(
              exporting
                directory            i_download_directory
                receiving
                result               
m_exists
              
exceptions
                cntl_error           1
                error_no_gui         2
                wrong_parameter      3
                not_supported_by_gui 4
                others               5
                ).
              if sy-subrc eq and m_exists eq 'X' .
                concatenate i_download_directory '\' m_filenamefull into m_filename.

*   Download the Zip file to temp directory
                cl_gui_frontend_services=>gui_download(
                exporting
                  bin_filesize              m_size
                  filename                  
m_filename
                  filetype                  
'BIN'
                  write_bom                 'X'
                changing
                  data_tab                  mt_bintab
                
exceptions
                  file_write_error          1
                  no_batch                  2
                  gui_refuse_filetransfer   3
                  invalid_type              4
                  no_authority              5
                  unknown_error             6
                  header_not_allowed        7
                  separator_not_allowed     8
                  filesize_not_allowed      9
                  header_too_long           10
                  dp_error_create           11
                  dp_error_send             12
                  dp_error_write            13
                  unknown_dp_error          14
                  access_denied             15
                  dp_out_of_memory          16
                  disk_full                 17
                  dp_timeout                18
                  file_not_found            19
                  dataprovider_exception    20
                  control_flush_error       21
                  not_supported_by_gui      22
                  error_no_gui              23
                  others                    24
                  ).
                if sy-subrc eq 0.
                  <files>-updateflag 'D'.
                  append <files> to et_files.
                  continue.
                else.
                  append <files> to et_files.
                endif.
              endif.
            endif.
          endif.
        else.
          append <files> to et_files.
          continue.
        endif.
      endif.
    endloop.

    if i_zip_separately is initial and i_zip_files is not initial.
      refresh mt_bintab[].
      clear ms_bindata.
      ms_bindata mo_zipper->save( ).
      check ms_bindata is not initial.
      clear ms_drat.
      read table mt_drat with key langu sy-langu into ms_drat.
      if sy-subrc ne 0.
        read table mt_drat with key langu 'E' into ms_drat.
        if sy-subrc ne 0.
          read table mt_drat index into ms_drat.
        endif.
      endif.
      if ms_drat-dktxt is initial.
        if i_filename is not initial.
          m_filenamefull i_filename.
        else.
          concatenate sy-datum sy-uzeit into m_filenamefull.
        endif.
      endif.
*   Convert the XSTRING to Binary table
      call function 'SCMS_XSTRING_TO_BINARY'
        exporting
          buffer     ms_bindata
        
tables
          binary_tab mt_bintab.
      clear m_exists.
      cl_gui_frontend_services=>directory_exist(
        exporting
          directory            i_download_directory
        receiving
          result               
m_exists
        
exceptions
          cntl_error           1
          error_no_gui         2
          wrong_parameter      3
          not_supported_by_gui 4
          others               5
             ).
      if sy-subrc eq and m_exists eq 'X' .
        concatenate i_download_directory '\' m_filename '.zip' into m_filename.

*   Download the Zip file to temp directory
        cl_gui_frontend_services=>gui_download(
        exporting
          bin_filesize              m_size
          filename                  
m_filename
          filetype                  
'BIN'
          write_bom                 'X'
        changing
          data_tab                  mt_bintab
        
exceptions
          file_write_error          1
          no_batch                  2
          gui_refuse_filetransfer   3
          invalid_type              4
          no_authority              5
          unknown_error             6
          header_not_allowed        7
          separator_not_allowed     8
          filesize_not_allowed      9
          header_too_long           10
          dp_error_create           11
          dp_error_send             12
          dp_error_write            13
          unknown_dp_error          14
          access_denied             15
          dp_out_of_memory          16
          disk_full                 17
          dp_timeout                18
          file_not_found            19
          dataprovider_exception    20
          control_flush_error       21
          not_supported_by_gui      22
          error_no_gui              23
          others                    24
          ).
        if sy-subrc eq 0.
        endif.
      endif.
    endif.
  endif.

endmethod.

Enjoy!