I'm 99% sure the answer to my question is going to be 'you can't do that', but on the off chance I might have missed something, I'm going to ask it anyway.
I've set up my sales contracts with password protection so the base document (terms and conditons) can't be altered and the sales reps can only complete the necessary form fields eg customer name, address, prices etc. In the past, the reps have then printed the documents, scanned them back in and then emailed them to the customer (they had the earlier versions of Reader so couldn't save the completed forms). They are now all being upgraded to Reader 11 so will have the ability to save the completed documents and email direct to the customer.
I've now been asked, how do we stop a customer from changing info on the doc once it's been sent to them, mainly the price. The sales rep should check nothing has been altered once the form is returned, but is there anything that can be done to stop someone changing a completed document in the first instance? It's not an option to give the sales people unprotected documents and rely on them adding the security (which they wouldn't be able to do in Reader anyway I believe).