PDF file editor

You need to write an A4 PDF file editor.

The essence of the program is as follows: there is a PDF file; there is a framework in PNG A4 format with transparency; Nuno impose this framework on each page of the selected PDF file. The quality of the PDF file pages must be maintained.

Interface: open the program, select a PDF file, select a PNG file, press a button, get the file in the same place as the original PDF file with the additional name ".new.pdf";