The textures are preserved in the pdo from when the model was imported from a 3d modeling program. Pepakura converts the texture information into raw data, which is basically coordinates for colored pixels. Unfortunately, most of the time this data can not be recovered by conventional means (like opening the file in notepad and removing the 3d info and saving as .jpg).
Solution 1:
You can preview the material in the "Texture setting" window, change your desktop resolution to the lowest it can go, take a screenshot, then restore your desktop resolution, open the screeny in your image editor (photoshop) and adjust the image, crop out the texture, and save it. Open the model in pep, go to Texture setting, specify texture, and open the new texture that you saved. The texture will be more pixelated than the original, but I don't know another way to do it.
Solution 2:
Most printers have a print quality setting, reduce the print quality (dpi) and you may get the result you are looking for without losing detail in the texture.
Solution 3:
Find the modeler and beg for the texture.
There is a forum for game developers called
XeNTaX, They may be able to write a script to extract the materials from pdo files. They also have several tools to rip game models/textures/audio/video (educational purposes only, don't post/ask for game content).