How to digitally sign a form or PDF?

[Guest]

We currently have a process in place that tracks all of our deliverables and notifies our government clients when we have invoiced them.  We email them a message to let them know an invoice is ready to be approved.  They login to our site via a browser, view the invoice, and approve or disapprove it.  If approved a PDF of the invoice is created via ColdFusion and is sent to them.

There may be an upcoming requirement to have the client digitally sign the document.  This is where the fog begins.  How best to do this?  Assuming that each client will have a PKI ID (and that's a big assumption), how do they sign the document?  I know they can open the PDF and sign it, and then I can setup a ColdFusion-based form to allow them to upload it back to us, but is there any other way?

[Steve Sommers]

We use RightSignature.com; it works great and our customers like it. DocuSign.com has been trying to get our business as well. The advantage of DocuSign over RightSignature is that everything can be signed without the user leaving our site whereas RightSignature sends the user an email with a link to sign and then sends us the final signed document. Since we're not using DocuSign, I'm not sure if there are other pros and cons.