When a PDF is displayed inline using the Acrobat plug-in (Acrobat 7.1.0 Professional), the [vertical] scroll bars will not be displayed again in that tab. The problem does not occur with the native Preview PDF display. Has been observed with WebKit nightly builds and with the Safari 4 Beta. Steps to reproduce: 1) Navigate to a page which scrolls and has a link to a PDF. 2) Click on the link so that the PDF is displayed inline, in that tab, with the Acrobat plug-in. 3) Click back to return to the HTML page. Note that the scroll bars are now missing. I'm told that the affected tab will need to be killed. Observed using the Safari 4 beta on OS X 10.4.11.
The bug is not observed with a straight-forward (lots of <p>s in a narrow <div> with a link to a PDF at the bottom) demonstration page, but it 100% repeatable with the page we first encountered it on. I'll try to narrow a test case down.
<rdar://problem/6625207>
This is no longer the case.