Most file types are accepted, including .doc, .docx, .pdf, .txt, .ppt, .gif, and .png. The acceptable file types are the same everywhere attachments are available (proposals, job posts, messages, etc.). Here's the help article for more information. I've also shared your concern with the team, and one of our agents will assist you further. Thank you.
Sarah, it is not Upwork's intention that you use the platform for professional data transfers. Upwork intentionally has many restrictions on file transfers and intentionally alters files in many ways.
Instead, use FTP, Dropbox, WeTransfer, or any of dozens of file transfer tools. Even email may be more reliable. Upwork does not identify itself as a transfer tool and it is not the right way to transfer many, many types of files.
Sarah D wrote:
Everytime I try to upload my TIF photos to upwork for editing, the format changes to JPEG. How do I keep the TIF format?
If you have a contract in place with your freelancer, you can do as Preston suggests and use a file transfer site. You can also send files directly to the freelancer. But also, freelancers can take jpeg files and do whatever it is you need done, and then save them as tiff files to send back to you.