The form submission cannot be processed because it exceeded the maximum length allowed by the Web administrator. Please resubmit the form with less data.

Step 1: Go to Central Administration - Application Management - Web Application - General Settings and change the Maximum Upload size.
Step 2: If step 1 does not resolve, ensure that you changed the maxRequestLength in the correct web.config. Double-check in IIS for the right virtual directory and the configuration file.
Step 3: Note that the MaxRequestLength is in KB. Do your calculations accordingly.
Step 4: There could more than one web.config files and it could be overridden. Check the appropriate one.
Step 5: refer this KB article.