I'm looking for a way to put an engineering stamp/seal on PDF's. I've made the image a "stamp" but need to add a digital signature that goes away if someone trys to make changes to the PDF. DOes Bluebeam do this? If so step by step how to would be great.
I don't think that it is possible. You may be able to "fake it" by creating a stamp which omits your name, license number, and date, then when you make a digital signature draw your box in the center of the seal and customize the text to include the above data. This would prevent someone from trying to resave with your digital signature in a non-compliant program.
Understand that anyone who opens the file as an image will effectively convert your signature (or your seal, even if you could make it as a stamp) into a bitmap. Then they can change data at will and save it. There would be no way to determine if a printed copy has been altered - just as it is with "real" signed print copies.
Licensing boards and uptight PE/RAs feel that this is often unacceptable, and yet they will gladly allow multiple photocopies to be made, which can be scanned, altered, and redistributed with identical ease. Digital signatures are better than physical ones because verification must be to a trusted source, but can be verified by anyone at any time. To verify an original signature under the "old" rules requires comparing, line by line, to a vellum original stored in the least habitable room (or basement, or storage shed) of the original firm.
I made a stamp which looks just like my signed seal, with a dynamic date field. I apply it to every page, and then put my digital certification on the first page of the set, just to the bottom right of the seal image. To date it has been accepted by every jurisdiction I've submitted, witht he exception of the Virginia Dept of Transportation, and that was only because I have a self-signed seal which I keep on my private server and they require a specific registrar instead. FWIW, they accepted a hand-signed (completely unverifiable) version of the sheets which were then scanned by me for upload into their tracking system.
Similar to what Jordan suggested, you can create a PDF Stamp from your seal and then place that on the PDF. After you have done this, "Flatten" the Stamps and place your digital signature over the top of them. This should prevent your seal from being accurately copied and keep it more secure.