A folded sheet carries four pages, and folding puts them in an order nobody would guess: the last page is printed next to the first, the second next to the second-last, inwards from there. Working that out is called imposition, and it is the whole job.
Drop a PDF, check the plan, and print the result double-sided with the flip on the short edge. Fold the stack in half, staple along the fold, and it reads from page one.
A booklet is the oldest trick in printing and still the one most often got wrong. Everything about it is simple apart from the page order, and the page order is not something you can work out by looking at the document. Print a twelve page report two-up and fold it and page 1 ends up on the back cover, page 2 on the front, pages 3 and 4 immediately inside them, and nothing after that anywhere near where it belongs.
What imposition means, and what it is not
Imposition is the arrangement of pages on a printing sheet so that the sheet, once folded and trimmed, reads in order. It is a printing term rather than a software one, and it predates the PDF by about five hundred years. The practice is as old as the folded book.
- Two sides, two pages on eachfour pages
- One fold down the middletwo leaves
- Stapled on the foldsaddle stitch
- Printed on a landscape sheetportrait pages
Putting two pages on one sheet is a different job, and worth naming because the two get confused. Pages per sheet keeps the reading order and shrinks the pages to fit, which is what you want for a handout or a review copy. A booklet breaks the reading order deliberately so that folding puts it back. One is for saving paper, the other is for making a book.
Pages reordered: 8 next to 1, 2 next to 7, and so on.
Printed double-sided, then folded down the middle.
Reads in order once it is folded and stapled.
Looks wrong in a PDF viewer, which is the point.
Pages kept in order: 1 next to 2, 3 next to 4.
Printed on one side or both, no folding involved.
Reads in order flat on the desk.
Looks right on screen and stays right.
Where the order comes from
Take an eight page document and one sheet of paper. Fold the sheet and you have four faces, so two sheets cover the job. The outer sheet wraps around the inner one, which means its front carries both the cover and the back cover: page 1 and page 8, side by side, with page 8 on the left because it will swing round the back when you fold.
Keep going inwards and the pattern is fixed: first with last, second with second-last, third with third-last. That is all the arithmetic there is, and the only thing that makes it fiddly is remembering that left and right swap when you turn the sheet over.
Printing it without wasting half a ream
The imposed file is landscape, two pages wide, and it has to be printed on both sides of the paper. The setting that matters is which way the printer turns the sheet over between the two sides, and it is the single most common way a booklet goes wrong.
Print double-sided
If the printer cannot do it by itself, print the odd-numbered pages of the imposed file, put the stack back in the tray, and print the even ones over them. Work out which way up the tray wants the paper before you commit forty sheets to it.
Flip on the short edge
Also called short-edge binding, or tablet. The sheets are landscape, so a short-edge flip turns them left to right, which is what the imposition assumes. Long-edge binding will give you a booklet with every second page upside down.
Test with two sheets
Print the first two sheets, fold them, and look for page 2 behind page 1. Thirty seconds and two sheets of paper, against reprinting the lot.
Fold and staple
Fold the whole stack in half together rather than sheet by sheet, so the pages line up. A long-arm stapler reaches the fold; an ordinary one does not, so swing it open flat, press it down through the fold from the outside onto a rubber mat or a stack of card, and bend the staple legs over by hand.
Adobe's own description of printing booklets from a layout program covers the same ground from the other direction and is worth a look if you want to see how a professional tool words the same settings.
Sheet size, and the A3 problem
Two A4 pages side by side make an A3 sheet. That is simply what A sizes do, and it is why a booklet of full-size A4 pages needs a printer that takes A3, which most homes and many offices do not have.
So there are two answers and the tool offers both. Automatic doubles the page width and leaves the pages untouched, which gives an A3 file for a print shop or a large-format printer. Naming a paper instead fits the pages into half of that sheet, so A4 pages on an A4 sheet come out A5: a proper pocket-sized booklet, which for a programme, a menu, a zine or a set of instructions is usually what was wanted anyway.
Automatic keeps every page at full size.
Naming a paper fits two pages onto it.
Pages are embedded, never rasterised.
The margin setting pulls each page in from the edge of its half, which matters because almost no printer prints to the edge of the paper. Five millimetres is enough for most, and if your pages already have generous margins you can leave it at none. If the pages themselves need trimming down first, cropping them before you impose gives a cleaner result than adding a margin here.
Thick documents, and why one fold is not enough
A single fold works beautifully up to about eight sheets and then starts to fight you. The stack no longer closes flat, the staple struggles, and the innermost pages push out past the outermost ones so the fore edge is a staircase rather than a line. This is normal, it is called push-out or creep, and a print shop deals with it by trimming the fore edge after folding.
The answer for anything thicker is to stop folding the whole document at once. Fold it in sections of eight or sixteen pages, then stack the folded sections in order. That is how every book on your shelf is made, and it is what the section setting does: the document is divided into groups, each group is imposed as its own little booklet, and the sheets come out in the order you need to fold them.
A last section shorter than the rest is padded on its own rather than to the full section size, so a twenty page document in sections of eight comes out as eight, eight and four: five sheets of paper rather than six. The plan shows the count before you build.
Binding on the other edge
A document that reads right to left, which covers Arabic, Hebrew, Persian, Urdu and traditional Japanese layout, binds on the right rather than the left. The sequence of pages does not change at all. What changes is which half of each face they land on: page 1 goes on the left of the first sheet instead of the right, and every pair mirrors with it.
That is one checkbox, and it is worth getting right, because a right-to-left booklet imposed left to right is readable only by starting at what feels like the back and working forwards. The plan updates as soon as you tick it, so the mirroring is visible before you print.
Why this runs in your browser
An imposition tool is an odd thing to upload a document to. The file is often a draft, a programme for an event, a school newsletter or somebody's manuscript, and none of those improve by taking a trip through a server to have their pages rearranged. The arithmetic is a few dozen lines and the page handling is a library your browser already has.
So the document is opened in memory, the pages are embedded into a new one, and the result is checked by reopening it with the same engine before it is offered to you. Nothing is transmitted, nothing is stored, and closing the tab is all the cleanup there is.
The tool is right above
Drop a PDF, check the plan sheet by sheet, print it double-sided and fold.
Common questions
Page order, printer settings, and the two things this deliberately does not do.
01Why is page 8 printed next to page 1?
Because folding turns the sheet inside out. The outermost sheet wraps around everything else, so one face of it has to carry the first page and the last page side by side. Work inwards and the pairs are second with second-to-last, third with third-to-last, and so on. The imposed file looks wrong in a PDF viewer and reads correctly the moment it is folded.
02Which double-sided setting do I choose?
Flip on the short edge, which some drivers call short-edge binding or tablet. The sheets are landscape, so a short-edge flip turns them left to right, which is what the imposition assumes. Drivers disagree about the labels, so print two sheets first, fold them, and check that page 2 is on the back of page 1. Two sheets is a cheap way to find out.
03My printer only takes A4. Can I still make a booklet?
Yes. Choose A4 as the sheet size and the pages are fitted two to a sheet, so an A4 document comes out as an A5 booklet on A4 paper. The alternative is to leave the sheet on automatic, which gives you an A3 file for a print shop and keeps the pages at full size.
04What if my document is not a multiple of four?
Blank pages are added at the end, which is where a reader expects them. A folded sheet carries four pages and nothing can change that, so a 10 page document becomes 12 with two blanks after the last page. The number added is shown in the plan before you build anything.
05How many sheets can one fold take?
Fewer than people expect. Past about eight sheets the stack stops closing flat and the inner pages start to stick out past the outer ones. That is what the section setting is for: fold in groups of 8 or 16 pages, then stack the folded groups in order, which is how anything thicker than a pamphlet is actually made.
06Does it compensate for creep?
No, and it says so rather than pretending. Creep is the shift printers apply to inner pages so the fore edge lines up after folding, and it depends on the paper you are using and how many sheets are in the fold. A print shop trims the fore edge instead. For the pamphlet-sized jobs this tool is for, it does not show.
07Is the text still selectable afterwards?
Yes. Each page is embedded as a vector form rather than rendered to a picture, so the text stays text, it prints at the printer's own resolution, and the file does not balloon. Links and form fields do not survive, because an embedded page is only the drawing.
08Is anything uploaded?
No. The document is read, imposed and written in your browser, and the result is checked by reopening it before it is handed to you. Nothing is transmitted and nothing is stored.