Windows 7 x64
Adobe Acrobat X Pro (Tested with 10.1.2, 10.1.3, & 10.1.4)
Internet Explorer 8
Display PDF in browser is checked
Display in Read Mode by default is not checked
We use Topaz signature pads, and when users try to sign a PDF inside the browser the "Sign Document" button is greyed out. We have to right click the PDF (still inside the browser) and open up "Page Display Preferences" and then the "Sign Document" button works. We've also noticed that clicking "Time Stamp Document" allows the Sign Document button to work.
I just tested this with Acrobat XI and it's working fine. So it appears to be a bug with Acrobat X?