For optimal print quality, we require a minimum of 300 DPI (dots per inch) at 100% print size. Images that are taken from the web usually are saved at 72 dpi and will usually never be high quality enough for printing. Low-resolution files may be printed as-is upon your request but we can not be responsible for poor appearance.
Tip for PDF files: Look at your artwork at 250% zoom. The quality you see at 250% zoom is very similar to how your artwork will appear after printing.