After ITA - is it possible to upload any additional documents?

[fl_pie]

I would like to provide some extra documents to CIC. However, it seems that it is only possible to provide the documents they ask for explicitly and a letter of explanation. Is there any way to provide an additional document, apart from merging it together with the letter of explanation?

 

[fl_pie]

In case anyone else would have the same problem and be interested what I did - I attached the document to the letter of explanation and uploaded the two as a single PDF file.