Sorry, the iPad version of Safari doens't have access to your filesystem or other documents. It is sandboxed for security and by design of the iOS. I'm sure some of the sites you wish to submit to don't have an alternative method (aside from perhaps via an email).
The webpage form cannot choose a file to upload since the Safari on iPad doesn't have direct support for file access. If you could upload to an FTP there are programs to do so. Otherwise, I'm not sure of a good method. Being Jailbroken may help in accessing your documents using iFile (but it doesn't help in getting it into the form field for submitting to a site).
You could search if there is a 'browser' that allows access to dropbox or some other place you may keep your resume. That may work, but I'm currently unaware of any browser option that will do so on the iPad.
A last ditch effort if you have access to another desktop computer is to 'remote access' the desktop screen and have your resume on that machine. Use the desktop's browser to get where you need and submit. You could use Logmein, iTeleport or one of the other less expensive screensharing/remote screen applications.
I have tried many and really think the polish of the two mentioned above are the best. Although I haven't kept up on the updated versions of others which may have improved over time, money may be a factor and the two are pricey. There are cheaper alternatives, if you are on a local wifi network its easy and pretty quick. If you are wanting to access the machine from the internet as a whole, be cause the software supports that natively and doesn't require manual port-forwarding or NAT translation.
Good luck.
