Write-protect your document

If you don’t write-protect your document, then someone can upload the whole file to their site and change it however they want (including editing out your links.)

—-TL;DR—-

Ok, ok. Look, PDF SEO ain’t too hard. Just follow this checklist:
Always use text-based PDFs
Set your title in the document properties
Set an SEO-friendly URL/filename
Do good SEO
Keep the file size light
Avoid duplicate content
Set the other document properties too
Touchup the Reading Order
Don’t save as the latest Acrobat version
Write-protect your document

Let me know in the comments if I missed in any PDF SEO FAQs.

–TTFN.