How to convert a .pa file into some other format that would be readable without Print Artist?
You could convert those files into PDF by installing a virtual PDF printer (there are lots of these, e.g. 'CutePDF') and executing File -> Print from within Print Artist. Then you just pick the PDF printer from the list and specify the file name.
You can use CutePDF, or PDFOnline, or PDFPro, to convert these. You will find CutePDF & PDFPro here in SI, but PDFOnline is a online tool, not always free. Although the others are also shareware.