What 148 × 210 mm means
A5 is a finished paper size. It does not identify a ring pattern, disc pattern, printable area or binding system.
The builder preserves these finished dimensions and will not silently scale the page to make an incompatible imposition fit.
Choose a source sheet and binding clearance
Print directly on 148 × 210 mm A5 paper, or center one page on A4 or US Letter. Two-up works on landscape A4 because each cell is 148.5 × 210 mm. It does not fit two-up on Letter because each 139.7 mm-wide cell is narrower than the 148 mm page. The builder rejects that combination instead of scaling it.
Centered and two-up files include crop marks where there is room outside the finished page. A mark is omitted where a source-sheet edge is already the finished edge; this does not change the page dimensions.
The inner content margin moves writing areas away from the selected binding edge. It is content clearance, not a punch-hole coordinate or a promise that a particular punch will fit. Trim first, then align the finished sheet with the punch maker’s physical guide.
Run one measured test
Download a one-page test before committing to a full run. In the print dialog, choose the paper named in your plan, turn off Fit or other scaling, and measure the calibration mark. A mathematically correct PDF cannot predict a printer driver, printable area, feed path, or borderless setting.
After trimming, measure width and height before punching. If the result is off, correct print scaling or the selected source sheet; do not compensate by guessing new page dimensions.