This surprised me as well. The system rasterizes uploaded PDFs at 200DPI, so there appears to be no reason to upload a PDF. It will always be better to export carefully prepared graphics at 300DPI manually.
When you block a person, they can no longer invite you to a private message or post to your profile wall. Replies and comments they make will be collapsed/hidden by default. Finally, you'll never receive email notifications about content they create or likes they designate for your content.
Note: if you proceed, you will no longer be following .