PDF Download opens up in wrong browser window Answered
The target window for opening the PDF window is called "_new". This isn't right - it should be "_blank" to open in a new window. Using "_new" means that all PDFs opened open up in a browser tab/window called "_new" and so they all open up in the same window and overwrite each other if you open up more than one at the same time.
Available target names are described here:
Should be a quick fix!