You can print the .pdf file to another .pdf file using any PDF writer and remove the security.  However, my malpractice insurance carrier will NOT let me send any tax returns directly to a 3rd party, especially and lender.  It has become common (and unfortunate) that by doing so the bank could sue you for a default on the loan.  Same concept with verification and other letters.  Be careful.

And I would not send an unprotected tax return to anyone.

@dascpa  Always, always, always, send the password protected pdf to your client.  Your client can then forward the pdf to the banker if they so choose.  The banker should be able to open the security protected pdf per the instructions contained in the body of the email using information that the banker should already have on file at the bank.