Just a heads up - found after analysing a reported issue. If you use Microsoft's 'Print to PDF' take care if you print 2D drawings to the same folder as your source files - it is all too easy to select an existing file name in the folder - this will be overwritten by the PDF, BUT the file extension will be left as whatever it previously was. So you end up apparently without the PDF (it is there, but with wrong file extension), AND you have what seems to be an Alibre file that errors when you try to open it (filealreadyexists error) because it is actually a PDF, not an AD file at all. The bonus is that you've lost your design file ! The only other virtual PDF printer on my system automatically appends the correct file extension, so avoids this issue.