submitForm fails for large PDF

We are using the JavaScript submitForm method to submit the form to a specified URL. The reason we do this is to send the PDF to our server. This works fine for most PDFs but larger ones are failing without any error given. Here is what the code looks like.

var return_msg = submitForm({ cURL: "urlToPost", cSubmitAs: "PDF"});

app.alert(return_msg); <- returns true

Is there any way to use submitForm for large files?