Acrobat Pro is $20/month. This is free.
or drop a PDF here
PDF only · Up to 50MB · Free
The problem
Adobe wants you to subscribe to Acrobat Pro at $20/month just to add a signature to a PDF. You need this feature once. Maybe twice.
The fix
Upload your PDF. Sign it. Download it. Free. If you need someone else to sign it too, that's $5. No subscription, no Adobe ID, no Creative Cloud.