Ok, get this.
I have been assigned to write an html form to be EMAILED to clients so that they can fill it in and submit it FROM THE EMAIL CLIENT! apparently emailin
There are only two possiblities: first one the mail client must have a php runtime environment to run the php script locally, also an embedded mail server - which isnt the case for the most of them. Second one is that your mail client acts like a browser and displays the form (which is located still on the internet) in his mail viewing window (which is perhaps possible but i dont know any common mail client doing this).
So you either submit a link to the form or you construct the mail this way, that there're placeholders to be filled and submitted like a normal mail response.
This is not a good idea on many fronts:
Not all email clients will support a form post from HTML see: http://www.campaignmonitor.com/blog/post/2435/how-forms-perform-in-html-emai/
No clientside validation
How are you getting data from PDF form submission? You can get expensive form tools from Adobe: http://www.adobe.com/government/forms.html
Some spam / av checkers will dispose of form based emails.
It's generally bad idea. Most email clients only allow limited HTML, with limited CSS and without any JavaScript at all. See: http://www.sitepoint.com/code-html-email-newsletters/
Many mail clients will not allow submitting any form (at least with standard security settings).
This idea is plainly wrong. You're creating a phishing vector for your company which could expose them to huge legal liability. Just ask them how much money they are going to be putting into the legal defense fund in order to pay out for the lawsuits they are going to lose.
An adobe pdf server is about the only reasonable method for doing this, but that takes lots of cash and work on your network to support a new type of server.