Is there a SuiteApp or something that will allow us to add the signature of the sales rep selected on the sales transactions to the advanced pdf templates?

If you require legally binding e-signatures on your documents, you can use docusign, adobe e-sign and few other Netsuite ready e-sign providers. Otherwise you can have a custom image type field in your sales rep's employee record and then source this image as the signature image in advanced PDF. It works I have done this multiple times for PO and quotes.

For the DocuSign, Adobe e-sign, etc., how does that work? When I print the quote, I would have then the option to put my signature/initials? And this is every time I need to print something or can it be automated as well?

I've used Docusign in the past. Our company would send out any new sales orders along with the contracts through the Docusign connector within NS so customers would review their orders and then sign the documents electronically, then all the signed docs would sync back as part of the SO on NS.

seems like you are looking for signature on a printed copy, then follow my 2nd step. Note it is not going to be a legally binding signature.

Thanks both. Actually, were already doing the second option mentioned by @Sam-I-Am. We're just looking for alternatives.