I cannot open pdf attachments directly from a mail message in PMail (I just upgraded to ver 4.8 hoping it would solve the problem but it didn't). Images (jpgs, pngs) open in Windows Photos, and Word/Excel docs open in MS Word and Excel. I haven't tried any other file types because these are pretty much all I would receive as attachments. I'm pretty sure that in the past, pdfs did open in Adobe Acrobat Reader directly from PMail. I can save the pdf attachment and then open the saved file in Adobe Acrobat Reader.
Any ideas?
Thanks.

What do you see when you do tools/options/content viewers for pdf files?
Does it show let windows deside or list a specific program to use?

There was a recent issue with the file name being over 140+ characters causing a problem, and since they .pdf was beyond the lenght Pegasus wasn't correctly processing it.

Since you said you can save file, and view it with Adobe, what is the lenght of the filename?

Are there any special characters in file name?

If you are double-clicking on the attachment, try selecting it and then clicking the "Open" button in the reader window toolbar.

If that works, then the problem may be that attachment preview is enabled. When it is, the double-click fails on some attachments.

It that does not work, we'll need to delve into content viewer settings.

Thanks. There was no filetype ".pdf" defined in the content viewers, so I've added it and now it works fine.