It seems to depend on whether the pdf is showing as an attachment or being viewed in the note. If I open from the attachment everything works as expected but if I open from the in note viewer then it opens as a different named file as you suggested. I am able to save as the original file and that works but I think the best route forward is to view as an attachment before trying to edit. Thanks for your help
I had this issue for ages and then a couple of months ago it just started working correctly - I could open a pdf from the note in drawboard edit and save back into the note no problem. Now I have had to restore Windows 10 and when I downloaded Evernote I have moved to 6.9 and it doesn't work any longer. I have deleted the files in the attachments folder but this hasn't made a difference. Any other ideas as it is such a messy experience to have to re save and then attach to the note after editing.