It is important to understand a term known as “OPI” which stands for “Open Prepress Interface”. This is where a low-resolution image is placed on the document page as a “placement holder” for a higher resolution image stored in a known location. The hi-res image, which is of course a much larger file, will be located and used in place of the lo-res picture at print time. If an image in the PDF is available on disk then a link to it will be created. If a PDF was generated with no OPI comments then the original image name and location will of course be unknown. If you choose “Save Missing Images” from the PDF2DTP Preferences a preview file will be conveniently created using the original name.