When using the non gmail app I cannot see pdf files when I am trying to attach one. It sends it fine if I go to the pdf document first, but if I am writing an email then want to attach, the document does not show up at all.
I know the gmail app let's you use Astro File Mngr, but the other app does not. It only uses MyFiles, as far as I can tell.
Go to the market & download the Astro File Manager. Anytime you want to attach, you now get a popup that asks if you want to use Astro or the default. Choose Astro and you will find all your pdf documents are attachment options. :-)