After investigating the issue I have found that it is a ASP.NET limitation put in place in order to prevent DOS attacks on web servers.
http://msdn.microsoft.com/en-us/library/system.web.configuration.httpruntimesection.maxrequestlength(VS.80).aspx
HttpRuntimeSection.MaxRequestLength Property
The maximum request size in kilobytes. The default size is 4096 KB (4 MB).
In order to bypass this limit you need to :
1.Open the Web.config file located in <Perfectforms Folder>/services/Web.config with a text editor
2.Add the following key under the <system.web> tag:
<httpRuntime executionTimeout="YourNewTimeInSeconds" maxRequestLength="YourNewFileSizeLimitInKBs" />
3.Save Web.config
4.Restart the Perfectforms application via IIS management console.
executionTimeout is not required but would be useful because large uploads might timeout.
maxRequestLength's maximum value is 2097150
