I am using Adobe Reader 9.4.4 with Max OS 10.6. I am unable to do a digital signature which is really frustrating. I've created a Digital ID. But when I click on Document-->Sign all the options are greyed out. It happens with all kinds of docs - I always check the document security settings to see if for some reason they are blocked, but usually are not. This has been a problem for a while, despite recent updates. Hope someone can solve this one for me! Thanks.
In order for Reader to apply a digital signature to a document, the document has to be Reader-enabled, which is a step that's done using Acrobat Pro or Adobe's LiveCycle Reader Extensions server-based product. Specifically, the document has to have the signature usage right. Note that usage rights are completely different than security restrictions.