A print-ready PDF of your photo book, free

Most photo book tools stop at a preview. The file a printer needs is different: it has to be the exact trim size of the book, carry enough resolution for paper rather than a screen, use the inks the press uses, and extend every edge-to-edge photo past the line where the guillotine cuts. Miss any of those and the shop either sends the file back or prints it anyway, and you find out when you open the box.

Kathaleaf's PDF is built to that standard from the start:

• 300 dpi throughout, the resolution presses ask for. Each photo is resampled from your original file, not from the preview you edited on.
• 3 mm of bleed on every side of every page. The PDF's TrimBox marks the cut, so the printer knows exactly where the page ends.
• Page geometry that matches the size you chose: A4 landscape or a 12-inch square, with 40, 50 or 60 interior pages plus the front and back cover.
• Text drawn into the page image, so there are no fonts to go missing or be substituted on someone else's computer.

Resolution is checked long before the export. When you import a photo, Kathaleaf flags it if its shorter edge cannot fill a full page of your book at 300 dpi. For A4 landscape that means about 2,480 pixels, which any recent phone photo has. A full page of the 12-inch square needs 3,600 pixels, more than the short side of a typical 12-megapixel phone photo, so that is where the warning appears most often. It is advice, not a block: a flagged photo still prints well smaller on the page, in a collage or beside another photo.

Before you export, the Proof stage shows every spread and both covers at print resolution, so you see exactly what the printer will get and can swap a photo while it is still easy.

Screens mix light in red, green and blue (RGB). Printing presses lay down cyan, magenta, yellow and black ink (CMYK), and they cannot reproduce every colour a screen can. If you hand a press an RGB file, someone converts it for you, with settings you never see. Kathaleaf does that conversion itself, carefully, and gives you the result.

The press file ends in -cmyk.pdf. Its colours are converted to FOGRA39, the standard condition for coated paper on an offset press used across Europe and widely by print shops elsewhere, using relative colorimetric rendering with black point compensation. In plain terms: colours that the press can print stay exactly as you saw them, colours it cannot are moved to the nearest one it can, and shadows keep their detail instead of filling in.

The second PDF is the same book left in RGB. Home inkjets and most office printers expect RGB and do their own conversion, so feeding them the CMYK file usually prints dull and muddy. Use the CMYK file for a print shop and the RGB one at home; the print guide explains which to use where in more detail.

A good file can still be printed badly. The most common mistake is scaling: a shop that prints “fit to page” shrinks the book and crops the edge of every photo. So with your PDF, Kathaleaf gives you a one-page specification sheet to hand over with the file. It states, in writing:

• the trim size in inches and millimetres, and the 3 mm bleed;
• the page count and the number of sheets, plus the covers;
• the resolution and the colour space, including the output condition for the CMYK file;
• to print at 100%, double-sided and flipped on the long edge, on 170–250 gsm silk or matte paper;
• to print one test spread before the whole book.

Nothing then depends on remembering the details at the counter or in an email thread. If the printed book does not match the sheet, you have it in writing.

Kathaleaf builds the PDF inside your browser. Your original photos are decoded, cropped and resampled to 300 dpi on your own computer or phone, converted to CMYK by a colour engine that runs locally, and written out page by page to a file you save. The photos are never uploaded to make it, and there is no render queue to wait in. You do need a free account to use Kathaleaf, and you sign in with Google or a passkey.

A large book takes a little while on an older phone, because every page is a full-resolution image. It is quicker on a laptop, and the file is yours to keep: export it again whenever you change a spread. Printing by Kathaleaf itself is coming later; until then the PDF is the finished product, and any printer can make it.