Recently when receiving a pdf file via email, I can view the pdf but when saving it shows as "locked" and requires the senders password. I need to fix this!

I did contact Vanguard about the password protected PDF and they explained it had nothing to do with Vanguard. Therefore, the password problem is with my macbook pro.

PDF files can be purposefully Locked by the original maker/ sender of the PDF for a reason including not allowing the receiver to modify or alter the contents of the file.

Bank, Credit Card Companies, Financial Institutions or Government Agencies often do this Lock Protection.

Sometimes this can be gotten around by opening the PDF and export as Copy. The Copy will be amended to the Original Name of the file so may to identify. Then open the copy file and see what happens. Notation - good and strong Lock Protect will not be removed when Exporting as a copy.

Vanguard is the Maker of the PDF or is Vanguard the e-mail Server Provider

I receive emails from my Banks and Credit Card companies via my E-mail Provider but the password protection is done by the Bans or Credit Card providers.

I would contact the sender unless you have this problem will all PDF's from different sources.