You can "lock" fields when the form is submitted but this only stops the user from making changes through the UI. If you knew what you were doing you coudl hack the PDF and change it. If you truely want to lock the form down you woudl need a digital signature. This will not stop a malicious user from changing th edoc, but when it was opened Acrobat/Reader woudl warn you that the doc has been changed form the original version. This is the real way to lock a form for legal purposes. By adding a digital signature you also increase the level of complexity of your solution (you have to manage and maintain the digital certs etc...).
Is simple locking of fields good enough for your app?
Thank you for the reply yes a simple situation will be fine as I am of firm belief that if they are that good they will find a way, as previously stated I am illiterate at this type of stuff the areas of concern are the radio button that I have merged together under the heading Assessment Type and Design Consultation, these buttons I would like to lock when they submit the form but still have access to them until that point in the event they decide to change there mind as remarked in the original post.
I would like to attach the file but can not seem to find an attachment button, if you would like the file please let me know, or let me know what i need to do to try and complete the situation i have will be greatly appreciated.