Preview automatically locking PDFs with password

For the past couple of months Preview has been password-protecting my pdfs and it's driving me nuts. When I first open the pdf with Preview I can view it with no issues but when I save it to my computer it locks the file so that the next time I open it I get a "This document is password protected" message. Ugh.

I've tested different PDFs and it only appears to happen with docs coming from an electronic signature program that I use for work (Docusign). I've used Docusign and Preview together for 10 years with no problem. I've asked other folks who use Docusign and they don't have this problem. Preview seems to open other PDFs without issue so it's obviously due to the fact that these Docusign documents have password security. Trouble is I have no idea what password Preview is creating for these docs. I've tried the passwords associated with Docusign, with my computer, even my Apple ID. Also tried the old standard "password" to no avail.

My current work around is opening them in Adobe Acrobat Reader and saving them which seems to remove the obstacle as Preview can then open the file. I really don't like using Adobe and hate the idea of Preview no longer being my PDF application but this is driving me nuts.

Any suggestions on how I can fix this and make Preview usable again?