|Why we need to manipulate your files|
When we receive your PDF file it should be set up at the size you want. For example if your book will be A4 size when it is finished then your page in the PDF file should also be A4 size.
The digital printing press uses large paper sizes than A4 and so we need to set you pages so that we print more than one page per sheet, if we were using an A3 sheet in the press we would print 2 A4 pages side by side to utilise the maximum area of the sheet of paper with the minimum amount of wastage, this keeps down the production cost and also helps the enviroment by ensuring that paper is not wasted.
We may also have to set up pages as what is know as "impositions" where the pages may have to be set up in a different page order so that when they are folded and bound into the final books the page then read in the correct sequence, an example of this would be saddle stitching when a 20 page document would be printed with page 1 & 20 opposite each other so that they would be in sequence as the front and back covers after the pages are bound.
Other common reasons for us needing to manipulate your pages are for us to put together the cover for the book where the size of the spine may not be known straight away and we need to adjust the spine size to accomodate the thickness of the book.
Sometime different finished sizes of the book are required which also requires us to do some work on the files.