Your options are to attach the document (and have it part of the PDF) or create a link to a file (where it is stored in a common location) and pass around the link. The link would have to to a web server (i.e. an HTTP connection). You will not be able to have a map to a drive or something like \\servername\folder as your link.
Thanks for the tip, it does make sense, however I do not know how to make this work. I'm interested in both solutions Paul. Can you expand on that please?
If you post your email address I will send you a sample of the programmatic way to attach a file.
For the link approach. I assume that you are referencing the files from a common location. So once we pick the file and know where it is we can create a link like http://servername/foldername/filename based on info we know and info we are passed. Then we simply construct the link name. I like to create a button (because it has a click event) and make it look like a link (no borders, same as the back ground and chnage the text and colour to blue). Does this make sense to you?
Paul sent me some code that did the trick however with a few changes I got it almost working as you described. Let me know if he doesn't get back to you.
I came across a user that is not able to add attachments. When I preview the PDF in designer it works perfectly. When I distributed the form for testing the user clicks on the add button and there is no prompt to select the files.