[Lynne]

When you says "open the thread I want the document to come up", do you mean you want the pdf to somehow be the thread contents (I don't think that is possible) or do you mean you want the attachment popup window to open for the user to either open the pdf in their browser or download it?

It sounds to me like you might to better to write some code where the user uploads a pdf file, it is uploaded to a directory on your site, and then you have a page which lists all the files in that directory and if someone clicks on one of them, it is either downloaded or opened in their browser. I'm not that familiar with all the mods here, especially ones dealing with attachments/files/uploads, but you can try searching in the Mods section and see what comes up.