You can only upload a PDF to Facebook groups and business pages, unless you convert the PDF to an image file.

How to Convert a PDF File Into a Photo for Facebook Uploading. If you want to share a PDF such as a quarterly report on Facebook, you can just upload it as a document to a Facebook group.

Adding a PDF to a Facebook Post. Involver's Scribd Facebook application lets you post PDF files to your Facebook business page to provide read-only documents for your company's customers.