upload a readable PDF file on Facebook:

• Only in specific cases and not on personal profile pages  does Facebook enable members to attach and upload PDF files to postings. You can submit the menu as a PDF file to your restaurant's Facebook business page. To do so, go to the page, click About on the left side, then More Info, then Add Menu, then select your menu's PDF.
• A PDF file can also be shared with other members of a Facebook Group. To do so, go to the Group page, click the More button, pick Add File, and select the PDF document to upload from the drop-down menu.
• You may also add the PDF document by clicking Files and then Upload File on the left side of the Group page.

Read More: Why can't I open PDF files?