Yes it is, there should be a "copy to my files" link on the download page for the file. There is also a copy endpoint in the api but not sure if this applies to files outside your account. Bear in mInd, if you copy a file and the original gets removed through an abuse report (DMCA) then it will be removed from ALL of rapidgator, not just the account that was reported.
If you use the api to upload then you just need the file size in bytes and the md5 from the download page, when you try and get an upload url using the same file size and md5 as a file that already exists on rapidgator it will just copy the file and return a download link instantly.