BindOps Help

Quick start

Load the PDF. Press Choose a PDF or drop a file on it. No PDF handy? Use a numbered sample PDF makes a 48-page test file with big page numbers.
Pick sheets per signature. 4 sheets (16 pages) is a common choice for 80 gsm paper.
Set the paper size and the duplex setting your printer uses.
Check the preview. Step through sheets with the Signature and Sheet menus or the arrow buttons. Numbers are page numbers from your PDF.
Impose and save. The file goes to your downloads folder.
Print double-sided at 100% scale. Turn off “fit to page” and booklet mode, because the pages are already placed.

Terms

Sheet	One piece of paper. Folded in half it gives four pages.
Signature	A group of sheets nested inside each other and sewn through the fold as one unit.
Spine	The folded edge. The opposite, open edge is the fore-edge.
Imposition	Arranging pages on sheets so they come out in order after folding.

Source

Setting	What it does
Pages to include	Blank means all pages. Otherwise a list such as `1-8, 10, 12-`. `12-` means page 12 to the end. Errors show under the box.
Rotate source pages	Turns every source page 90° or 180° before placing it, on top of any rotation the PDF already has.
Blank pages at each end	Adds 0 to 8 blank pages at the front and the same number at the back. Use for endpapers or a clean first page. The total is then padded to a multiple of 4 with extra blanks at the end.
Right-to-left binding	Swaps left and right on every sheet, for manga, Arabic and Hebrew books.

Signatures

Setting	What it does
Folded sheets per signature	1 to 12 sheets (4 to 48 pages), or the whole book as one signature.
Even out signature sizes	On: 9 sheets at 4 per signature become 3 + 3 + 3 instead of 4 + 4 + 1, so there is never a stub. Off: full signatures first and one short one at the end.

Total pages are always padded with blanks to a multiple of 4. The Blanks added figure in the stats shows how many.

Creep and paper

When sheets are nested, the inner ones stick out further at the fore-edge. Trimming fixes the edge but eats into the inner pages’ margins. Creep compensates: each sheet further inside moves its pages toward the spine by its position (outermost 0, next 1, and so on) times the creep value.

Setting	What it does
Work out creep from paper weight	On by default. Enter the gsm and pick the paper type. The app estimates one sheet’s thickness and uses it as the creep. The creep box shows the result and is locked. Turn off to type your own.
Paper weight (gsm)	Printed on the ream. Common copy paper is 80.
Paper type	How thick the paper is for its weight. Choose I know the thickness to type one sheet’s thickness in micrometres (µm).
Creep per nested sheet	In the chosen unit.

The estimate: thickness of one sheet = gsm × bulk ÷ 1000, in mm. The innermost sheet of an n-sheet signature moves in by (n − 1) × creep.

Paper type	Bulk (µm per gsm)	Example
Uncoated or copy	1.25	80 gsm ≈ 0.100 mm, 100 gsm ≈ 0.125 mm
Bulky or cream	1.5	90 gsm ≈ 0.135 mm
Matte coated	0.95	130 gsm ≈ 0.124 mm
Gloss coated	0.8	130 gsm ≈ 0.104 mm

These are typical figures. For the best result, measure a stack of 10 sheets with calipers, divide by 10, and use I know the thickness. Then print one signature, fold, trim, and raise or lower the value if the fore-edge is still uneven.

Creep matters most with thick paper or many sheets per signature. A 4-sheet signature of 80 gsm paper creeps 0.3 mm in total, which is hardly visible. A 12-sheet signature of 120 gsm uncoated paper creeps 1.65 mm.

Paper and printer

Setting	What it does
Paper size	A5, A4, A3, Letter, Long bond (8.5 × 13 in), Legal, Tabloid, or Custom. The sheet is always used landscape.
Units	Millimetres, inches or points. Changing it converts the values already entered.
Duplex	Flip on short edge is the usual setting for landscape sheets. Flip on long edge: the back sides are turned 180° in the file so they print upright.

If the backs come out upside down on a test print, switch the duplex option and save again.

Page placement

Setting	What it does
Scaling	Fit keeps proportions. Stretch fills the box and distorts. Original size places the page unscaled and does not clip it.
Position	Centered in its box, or snug to the spine.
Margins	Top, bottom, fore-edge and spine. The spine margin is per side, so the gutter at the fold is twice that value.

Bleed

Bleed is artwork that runs past the trim edge so no white sliver shows after cutting. Your PDF has to contain it already: export from your design app with bleed (commonly 3 mm). BindOps cannot invent artwork that is not in the file.

Setting	What it does
Bleed in your PDF	None: pages are trim size (default). Read it from the PDF (TrimBox): uses the TrimBox that InDesign, Affinity and Illustrator write when you export with bleed; each page is read separately. Set an amount: you type the bleed and the outer edge of every page is treated as bleed.
Bleed on each side	Only for Set an amount, in the chosen unit.

The real page (trim size) is fitted into its box on the sheet, and the bleed is drawn outward into the margins at the head, tail and fore-edge. Nothing is drawn across the spine, where the sheet is folded. The preview shows the bleed as a dotted blue outline.

Make the top, bottom and fore-edge margins larger than the bleed, plus about 4 mm more for trim marks. A red note appears when they are too small. If the page says No TrimBox found, your PDF was exported without bleed or without a TrimBox; choose Set an amount if you know it has bleed.

Marks

Marks print in light greys so they are easy to ignore or trim away.

Mark	What it does
Fold line	Light grey dashed line down the centre of the sheet.
Signature and sheet label	Small text in the gutter, such as `Sig 2/4 sheet 1/3 front`. It disappears when folded. Turn off if the gutter is too narrow.
Collation marks	A bar on the spine of the first sheet of each signature, stepped down the spine. With signatures stacked in order the bars form a diagonal, so a missing or misplaced one is obvious.
Trim marks	Short ticks just outside the fore-edge corners of each page, offset past the bleed, showing where to cut at the head, tail and fore-edge.
Sewing marks	Small dots centred on the fold at evenly spaced stations. Set the number (1 to 12) and the distance from head and tail. Use them to pierce holes.

Output

Setting	What it does
File type	One PDF, all signatures in order: print it in one go. One PDF per signature: files named like `book-sig-01.pdf`, better for printing one signature at a time and folding while the next prints.
Save to	A folder on this computer: files are written straight into a folder you choose. Browser downloads: the usual download (a ZIP when there is one PDF per signature).

Saving to a folder

Press Choose folder…, or just press Impose and save and the picker opens.
Allow the browser to write to that folder.
The files appear in the folder. With one PDF per signature they go into a new subfolder named after the book. Files with the same name are overwritten.

BindOps remembers the folder, so next visit it only asks you to confirm. Press Save again to write the same result a second time.

Saving to a folder works in Chrome, Edge and Opera. Firefox and Safari do not allow websites to write into folders, so there the Save to menu is hidden and files go to your downloads folder.

Printing checklist

Print one signature first on scrap paper.
Double-sided, correct flip edge, scale 100%, paper size matches the chosen paper.
Fold, nest, and flip through. Pages must run in order.
If the order is right but the backs are upside down, change the duplex setting and regenerate.
If fore-edge margins are uneven, raise the creep (turn off Work out creep from paper weight and type a value).

Grain direction should run parallel to the spine. Choose the paper orientation to suit.

Troubleshooting

Symptom	Likely cause
“Could not open that PDF”	Damaged or encrypted file. Re-save it from a PDF reader. Remove any password first.
Pages look squashed	Scaling is on Stretch. Switch to Fit.
Pages are tiny	Margins are large for the paper size, or the source page is much larger than the paper. Reduce margins.
Nothing saves	The browser blocked the download or the folder. Allow downloads for the page, or press Save again and choose the folder again.
Order is wrong after folding	Check the duplex setting and that the printer ran at 100% scale with duplex on.
Slow or out of memory	Very large PDFs (hundreds of pages with big images) need a lot of memory. Impose a range at a time with Pages to include.

Privacy

BindOps runs entirely in your browser. Your PDF is read on your device and the result is built on your device. Nothing is uploaded, and the app makes no network requests after the page loads. A folder you choose for saving stays on your device; the website cannot read what is in it.

BindOps by 5J Studio. Inspired by Bookbinder JS; no code from that project is used.