This might be caused if you filled out and signed the form in Acrobat (this is not a problem in Reader), and then saved
it without granting signature and commenting rights.
In order to do this (and remember these instructions apply *only* if you are
signing in Acrobat!):
- First complete signing the document. This will require that you save it as part of that process.
- Then click on "Advanced"->"Extend Rights for Adobe Reader". This will again require that you save it.
- Do not make any other changes on the document before uploading it to the website. Once the document is saved with "extended rights" then it will be signable by others using Adobe Reader.