FamilySearch.org's Photos program is about to take a new turn and allow PDF files to be uploaded. This new feature is in Beta testing. Click this link to get to the beta site. If you want some specific instructions about the process, see the blog post by Matt Wright entitled "Capturing and Uploading Document in PDF Format to Family Tree."
Very importantly, if you have already uploaded a photo of a document or other item, the designation can be changed to that of a document. At this point there is nothing in the announcement about using either photos or documents as additions to sources. I guess we will just have to wait and see what happens.