Please ensure you have followed these steps prior to sending the artwork :
1) Convert all text to outlines / paths (the exact terminology depends on your software).  Please include the fonts when you submit the artwork if you haven't managed to convert the text.
2) Ensure all images and relevant artwork are at 300dpi before designing the layout (we may ask you to submit higher resolution versions in some instances)
3) Include bleed on all layouts, it may slow down the setup of your order if we have to request new artwork from you. As a general rule, A6 and below require 1.5mm bleed on each edge, A5 and above requires 3mm on each edge.
4) Ensure that all artwork is clearly labelled (eg; JoeBloggs_Front.pdf, JoeBloggs_Back.pdf)

We also accept the following files (ensure you follow steps 1-4 above when submitting any artwork) :
*If would like to submit in a format not listed here, please contact us to make sure we can accept it.

Vector based artwork (preferred format type) :
Adobe Illustrator - .ai
Adobe Indesign - .indd
Corel Draw! - .cdr
Encapsulated Postcript - .eps (most vector art packages can export to this format)
Macromedia Freehand - .fh* (Problems are likely with this format, please send as a different format if possible)
Microsoft Publisher - .pub
Microsoft Word - .doc
Microsoft Powerpoint - .ppt
Quark Express - .qxd (Problems are likely with this format, please export as .eps file to minimise problems)

Bitmap based artwork (only use this format type if you cannot supply vector artwork) :
Adobe Photoshop Image - .psd (include fonts used and don't flatten text layers)
Bitmap Image - .bmp 
Fireworks PNG - .png (fonts must be included)
PNG Image - .png
JPEG Image - .jpg, - .jpeg
TIFF Image Document - .tif