We downloaded this client to test SFTP today: https://www.smartftp.com
The PDF files work perfectly when moved using their tool The byte sizes match the source and the PDF files open without errors.
We have also confirmed FileZilla works correctly also.
We need help working out why SFTP with PDF files at least fail using the current version of WinSCP.
We have also now tested this using ZIP and TXT files, and the same problem exists. The transferred file has different byte sizes than the source file.