How the kit maker works

From your PDF to the kit

1. Read. The PDF is read from your device into the page. The PDF reader (pdf.js) parses it in a separate worker, so the page stays responsive. Nothing is uploaded.
2. Pick. Each page shows as a tile, painted only when it scrolls into view and kept as a small picture until you close the PDF. You choose up to 12 pages and their order.
3. Lay out. The listing's title, benefit line and list, your chosen pages and your brand kit go into fixed templates for the cover thumbnail, page thumbnails and pins. The previews on the page are the same drawing as the files.
4. Export. The preview PDF, each image, or everything in one ZIP, made in the page and handed to your downloads. A long job shows a count and can be cancelled.

Previewfold lays out your own pages. It does not write, draw or generate anything. Every word on the images is one you typed, every picture is one of your pages or your logo, and the layout follows the rules below, the same way every time.

The rules, in the order they run

1. A file is read only if it is a PDF (its first bytes say so), 150 MB or smaller, and has 200 pages or fewer. A password protected PDF is named as such and not opened; nothing tries the password. A damaged PDF gets a plain message, and anything already open stays open.
2. Pages are painted on white, the colour they print on, so a page with a transparent background previews as it prints. No canvas larger than 16 million pixels is made; a page that would be larger is painted at a lower resolution and the page says which.
3. A listing needs a title of 1 to 140 characters, and may have a benefit line of up to 90 and a list of up to 8 lines of up to 60 characters each. An emoji or an accented letter counts as 1 character. Text over a limit is kept as typed, marked, and nothing is exported until it is shortened; nothing is cut to fit.
4. The brand kit needs a shop name of 1 to 40 characters; the tagline may be up to 80 and the watermark text up to 40.
5. Text never overlaps a page miniature: every template keeps text and pages in separate parts of the image.
6. Page miniatures keep their page's shape: never stretched or cropped. For 2 to 4 pages, every way of splitting them into rows, or into columns, in order, is tried, and the one that shows the most page area is used. Area is discounted when the miniatures would differ a lot in size, so 4 pages of a size beat 1 huge page beside 3 tiny ones (rows, and fewer of them, on a tie).
7. Titles wrap by words to at most 3 lines at the template's size. A title that needs more is set one step smaller (80 percent) with as many lines as the space holds; only if it still does not fit is it set smaller again, in 10 percent steps. On thumbnails and cover pages a title is never cut off. On pins, which are read at feed size, a title keeps to 3 lines: it is set smaller, down to 56 pixels, and if it still needs a 4th line it is shortened with an ellipsis and the page tells you, so you can shorten it yourself.
8. Every piece of text is checked against what it sits on. Titles and small text need 4.5 to 1 (WCAG 2 contrast). Below that, the text switches to black or white, whichever has more contrast, and the page says so beside the preview.
9. A logo whose visible pixels have less than 2 to 1 contrast with the colour behind it is set on a small plate of white or black, whichever contrasts more with the logo, so a dark logo never vanishes into a dark colour.
10. Characters a kit font does not carry, an emoji among them, are drawn from your system's own fonts, never as an empty box.
11. The preview PDF is made at the chosen resolution (72 to 150 dpi, 110 unless you change it). If it is over the size target, it is made again lower, as below, down to 72 dpi.

The watermark rule

Each chosen page is painted as a picture, the watermark is drawn into its pixels, and the page goes into the preview as a JPEG picture. The preview holds no text layer to copy and no watermark layer to remove. The cover and closing pages carry no watermark: they are your own branding.

• Diagonal repeat: the text repeated across the whole page at an angle.
• Centre single: one large line across the middle of the page.
• Corner tag: a small tag in the lower right corner.

Opacity is a whole percentage from 10 to 60. The watermark is drawn in your main colour if it reaches 3 to 1 on white, otherwise in black, with a thin white outline so it stays visible on dark pages. The text is your shop name unless you type another.

Sizes

Current marketplace sizes, with their sources, are on marketplace image sizes.

Worked example

The size target. A seller chooses 12 detailed pages at 110 dpi with the 20 MB target, and the first file comes out at 31 MB. Size grows with about the square of the resolution, so the next try is the dpi that should land 5 percent under the target, and at least 5 dpi lower: 83 dpi. The page then reads: “At 110 dpi the file was 31 MB, over the 20 MB target, so the resolution was lowered: 110 dpi (31 MB), then 83 dpi (18 MB). Saved at 83 dpi.”

The colour check. With the starting colours (main #1f5c4a, second #f2b84b), each frame decides like this:

• Clean: the title is set in #1f5c4a on the background at 7.8 to 1. The shop tag is black on #f2b84b, 11.7 to 1.
• Bold: the title colour does not reach 4.5 to 1 on the background, so titles are set in white (7.8 to 1). The shop tag is black on #f2b84b, 11.7 to 1.
• Soft: the title is set in #1f5c4a on the background at 6.2 to 1. The shop tag is white on #1f5c4a, 7.8 to 1.

Small text is held to the same 4.5 to 1.

What is kept, and where

Brand kits and listings are saved in this browser's storage as you work; a logo's file goes to the browser's own file store (IndexedDB), never into the record as text. Your PDF is never saved: only its name, size and page count are kept with the listing, so you can match it when you come back. A save is counted only once it reads back the same; a record this version cannot read is kept as it is and offered for download, never overwritten; a new logo is saved and checked before the old one is removed. If the browser blocks storage, the maker still works for the visit and says so once.

The free plan makes 3 listings a month, counted in this browser by calendar month in your own time zone. What counts is the product: the PDF (its size and the start and end of the file), the chosen pages and the title. The first export of a product in a month counts; exporting the same product again does not. Change any of those and it is a new product.

What it is not

• It does not write titles, descriptions or tags, and it does not draw or generate pictures. Previewfold lays out your own pages. It does not write, draw or generate anything.
• It does not upload anything or post to any marketplace. You upload the files yourself.
• It does not make copying impossible. A watermark makes a preview unattractive to copy, not impossible.
• It does not open protected PDFs or edit your PDF. The original file is only read.
• It does not check a marketplace's rules for you. They change; check them before you list.

Previewfold is not affiliated with Teachers Pay Teachers, Etsy, Pinterest, Canva or any marketplace.

Questions are answered in the FAQ. Ready? Open the kit maker.