I want to print a file to convert it to PDF format.

Because I need to custom the size of my document : 248x126 mm for a 2111x1072 pixels file.

I install a PDF printer (both doPDF v7 and PDFCreator).

In GIMP :
File > Page layout > Custom size

File > Print... > In the Picture parameters tab, the layout doesn't suite to my picture.

So I go back to
File > Page layout
but the paper format came back to A4 !!!
IT DOESN'T MEMORIZE THE PAPER FORMAT !!!

If I try to print (even setting my printer perfs), the PDF document is the same showed in the little layout window in 
File > Print... > In the Picture parameters tab

I tried every configuration possible, with doPDF and PDFCreator, I tried to create new print formats, but nothing change.

I tried with the print service of Windows and Photoshop, and it works. So I think it's a bug...