When I want to open a prt/asm file in PDMworks (old version!), I can't view it. It puts a window for me saying that I have to open the file. However, when I click on open/save, it shows me an empty edrawings. I click on cancel, it shows me a page with "navigation to the canceled web page".
I'm also thinking of a file version conflict. Note that when the files are too old compared to the SW version it happens that it is impossible to open them or at least only on some workstations (what is it related to, joker)
As PDM only supports versions n to n-2 of SW (PDM2016 compatible SW2014 to SW2016), I'm not sure that very old files are compatible (in our PDM2014 we have 2009 files that open without any problem, but I haven't done the test on PDM2016 that we will deploy soon).
The best thing to do is to convert the files in the vault during the software evolutions, the PDM conversion utility is very practical for that.