Hi,

Firstly, thanks for taking the time to convert a tutorial. Lots of people use Gimp so I'm sure it will be useful.

You should be able to attach a PDF, much the same way you attach a regular image. If you click 'Go Advanced' under the comment box, then use the 'Manage Attachments' section (see instructions here - these are for images, but I think it should be the same for PDFs). The only problem might be with the file size. The limit for PDFs is 10mb, I believe. Is your file larger than that, as that might be a problem.

I sorta have the feeling there may have been an issue with PDF uploads, but I might be misremembering, or it may have been sorted. Either way, give it a try, and if you can't get it to upload, post again and let us know, and we can take a look.