In order to start printing a design, we need a print-ready file. Not all file types can be processed by us. Most formatting programs have their own file format. You can recognise it by the extension at the end of the filename (for example: .doc, .xls, .psd, .pub, .ai, …).
We can only process your files if you provide them in PDF or JPG.
This way you limit the size of the file and you maintain the high quality of the layout.