Is this the place to add an errorreport - ealier it was on a forum on sourceforge?
In PDFArchitect, You can rightclick on a page in the panel on the left, and select Export.
Then You get a dialog, and can choose to save the page as eighter JPG,PNG or TIFF. But if You save a page as a jpg-file, it is saved with the extension .jpg, but it is actualy a png-file.