The add pdf button in the post editor is not working properly but it will after I update the forum software later this week.
For now you can post PDF files by simply enclosing them in bbc brackets. Depending on your version of Adobe, they will act just like you are used to. For instance hovering your mouse near the bottom will allow you to save, print, zoom, etc.
[pdf]urltoyourfile[/pdf]
I noticed that if you modify the post after it's been posted the file show in the edit screen just like in the post. The tags call a command that displays the file.
if you edit the post the absolute link is shown instead of the file. I have a feeling it will do the same with this quoted reply as well.
This anomaly will also be fixed in the update. I've already tested it on another site and it works famously.