Add blank pages where duplex needs them
Duplex printing is a parity machine: sheet 1 carries pages 1 and 2, sheet 2 carries 3 and 4, and it cannot be argued with. So a chapter that starts on a left-hand page, or an odd page count that wastes the last back, can only be fixed inside the file — by inserting blank pages at exactly those points. Tell this tool where; it rewrites the PDF in your browser and uploads nothing.
Right-hand page = odd page number. List where your chapters or sections begin.
For anything else — a deliberate empty spread, a section for notes.
A worked example
Say chapters start on pages 1, 24 and 57 of a 100-page book, and each should open on a fresh right-hand (odd) page:
- Page 1 is already right-handedOdd page, fresh sheet. The tool leaves it alone — there is nothing before it to shift.
- Page 24 is even — a left-hand pageOne blank after page 23 pushes chapter two onto page 25: odd, right-handed, and chapter three now starts at 58, not 57.
- The tool carries that shift forward58 is even too, so a second blank goes in — and the tool counts the new total, 102, so the last sheet's back is a deliberate blank rather than an accident.
The two boxes, and when each is right
| You want | Type into | The tool does |
|---|---|---|
| Chapters or sections to open on right-hand pages | The first box (page numbers where sections begin) | Inserts the minimum blanks that make each listed page odd, carrying shifts forward. |
| A blank at exact positions — end of a part, room for notes | The second box (pages to follow with a blank) | Inserts one blank directly after each listed page, no cleverness. |
| An odd total to come out clean | The tick box | Pads one blank at the very end, so the printer's last flip lands on purpose. |
Questions people actually ask
Why is a right-hand page an odd number?
Convention: page 1 is a right-hand page, and each opened spread adds two — so left pages are even and right pages are odd. Books whose chapter openings respect this read settled; ones that don't read like a photocopied handout.
Won't blank pages look like a mistake?
Not when they sit at the end of a section — every professionally made book is full of deliberate blanks, and a right-hand chapter opening is the whole point of them. The only blanks that read as accidents are the ones you didn't choose.
Does my PDF get uploaded anywhere?
No. The pages are copied into a new PDF in your browser's memory with the blanks inserted, and handed straight back. Nothing crosses the network.
Can I delete pages too?
This tool only inserts. For deleting, any PDF editor will do it — but if you are deleting to fix duplex parity, count twice: removing one page flips the side of every page after it.
My pages are different sizes — what size are the blanks?
The tool takes the size of the file's first page. Mixed-size PDFs are rare (and usually an accident worth fixing first); if the blanks come out wrong, that is the reason.
The studio does this arithmetic for chat books automatically.
See it work — freeThis is one of the tools — or see everything we’ve written.