CORE_FILE_READ CORE Endpoint
  /rpc/core/?method=CORE_FILE_READ  
  Reverse of CORE_FILE_MANAGE in that it takes an existing attachment, and returns its text  
  If you just want the contents of an attachment returned in an Advanced Search format try CORE_ATTACHMENT_READ
  PARAMETERS TYPE NOTES
  Base64 Text (1) Y / N [default]. If Y, the contents of the file are returned in Base64
  DataOnly Text (1) Y / N [default]. If N, the response is just the file data, instead of being returned in a standard response.
  Id Numeric Mandatory. Id of the attachmentLink.
  RETURN  
  filedata Text