You might open the PDF file in Adobe Reader and print it there to a Postscript file (setting page size to “Custom…” and choosing a bigger than current), but this does not allow free placement, instead Adobe Reader always centers the output on the paper.
Instead, use xpdf. Start it and set the desired print page output size simulteneously:
xpdf -paperw 3444 -paperh 4252 -z page infile.pdf
xpdf expects the sized in Postscript points: 1 point = 127⁄360 mm = 352.7 µm. Sad enough, xpdf also centers the output on the page.
But we have another trick: calculate a page size where you can cut out your desired page size after the content gets centered on it. Generate a PDF with that size using either xpdf or Adobe Reader, printing to file with them and re-destilling to a PDF file. Then, open it in Adobe Reader and bring place the view (i.e. what you see on your screen) exactly so that it covers the page size you want the document to have. You need to set the zoom level for that (which is also possible in 0.01% steps!).
Then print in Adobe Reader to a Postscript file and select “current view”. Adobe Reader informs you about the size of the view in the print preview, so that you can adjust your settings.
And to conclude, destill the Postscript file again to PDF using ps2pdf.