Here I prepared a little demo .pdf showing a design (which i created many moons ago,
so it serves only as an example for this document) and at the bottom left
my qualified digital signature. The document was also timestamped after
signing, with an EU Trustlist qualified timestamping service. Not sure what services
are available in the U.S. to do the same.

https://ufile.io/c9jrevsp

And additionally one can detach sign the model file with GnuPG and timestamp
it too via the blockchain i previously mentioned.

You can verify the .pdf with the free Adobe Reader DC or at this European
site:

https://ec.europa.eu/cefdigital/DSS/webapp-demo/validation


Regards
Stefan