Yes you can! Just like video and images, you can stack and compare multiple versions of a PDF. Simply drag the new version over the top of the old one to upload, or click on the '...' menu in the project thumbnail to find more upload options.

Team members can compare two versions side-by-side via the version selector at the top of the asset viewer window.
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​Note: new versions will not automatically be sent to your reviewers, you will need to re-share the new version