How much margin should I leave for Wire-O Binding?

As indicated below, the binding must be taken into account when designing the file for a Wire-O Bound Book. On the top, bottom, and non-spine edges, the margin should be a minimum of 0.25". On the binding edge,  0.27" of margin for the binding plus 0.25" of safety will ensure both that nothing gets cut off, and that the content looks centred.

Even though it will actually be slightly off centre, the reader will judge from the edge of the bindery punches rather than the actual spine edge of the sheet. Therefore it is always important to include the margin for binding in any margin calculations, in case more margin than the recommended minimum is desired. If, for example, a 0.5" margin is required, then the spine margin would be 0.5" plus the 0.27" for the binding, for a total of 0.77", but only on the binding side. On the other three edges, the margin would be 0.5".

The other aspect of binding that needs to be taken into account is the fact that the spine edge alternates on the "even" and "odd" pages. This is independent of any actual page numbers that are added to the artwork, as the numbers can vary based on whether the cover is included, whether there's a table of contents, if there is a section at the beginning that is numbered separately, etc.

Suppose the front cover is designated as "page 1", the inside front cover would be "page 2", etc. This would mean that for a conventional book that is read from left to right, all of the odd pages starting with the front cover would have the spine on the left-hand side, and all the even pages starting with the inside front cover would have the spine on the right-hand side.