If you are asking about using the PDF button in Manager, then the answer is as @lubos told you in this post: some of the coding in your theme is not supported by Manager’s PDF generator.
If you are asking about the image being split an repeated in a pdf: tell us the type of image file your are using (jpeg, gif, etc.) and the size (width in pixels, height in pixels, DPI), so that someone can try an replicate the problem.
Keep in mind though, that there is the possibility that the CSS declarations used in your theme may not be supported in your print-to-pdf creator, as they are not supported in Manager’s pdf generator. I’m not sure where you would find the answer as to which declarations are supported in your pdf printer.