Turn a PDF into one long image, and when one image is the wrong idea

When a long image is worth it

A long image scrolls like a web page: no PDF viewer, no page flipping, the whole thing in a chat bubble or a notes app. That works well for a 2 or 3 page menu, a short itinerary, a receipt that runs over 2 pages, or 2 slides that belong together. It works badly for anything long, anything someone prints, and anything with small print, for reasons the maths below makes plain.

The maths first

An A4 page converted at 150 dpi is 1240 x 1754 pixels. Stack pages and the width stays, the heights add up:

Pages stacked (A4, 150 dpi)	Image size	Shape
2	1240 x 3508 px	about 1 : 2.8
3	1240 x 5262 px	about 1 : 4.2
5	1240 x 8770 px	about 1 : 7.1
10	1240 x 17540 px	about 1 : 14

The JPG format cannot go past 65,535 pixels on a side, which is about 37 A4 pages at 150 dpi. Long before that, apps shrink the picture to their own maximum, and the narrower the shape, the smaller the text ends up. That is why 150 dpi is the sensible ceiling here: 300 dpi doubles every number in the table and the app throws the extra away.

Way 1: a tall strip, stacked in an image editor

1. Trim the margins first (optional). Crop PDF with Trim white margins cuts every page to its content plus 3 mm, with Same size on so all pages stay the same width. Narrower pages mean bigger text once the strip is shrunk on a phone.
2. Convert the pages. Drop the PDF on the converter above, leave Resolution at 150, type the pages in Pages (for example 1-3) and press Make the images. You get menu-1.jpg, menu-2.jpg, menu-3.jpg in a zip, named in page order.
3. Stack them. Open the first image in an image editor, make the canvas taller by the height of the other pages (in GIMP: Image, Canvas Size; in Paint on Windows, drag the canvas’s bottom handle down), and paste each next page below the last. Leave a few pixels between pages if you want a visible gap.
4. Export as JPG. Quality around 85 keeps text clean. Check the size before you send it: 3 pages of text land in the hundreds of kilobytes, 3 pages of photos can be several megabytes.

Crop PDFTrim the white margins so the text shows larger. Free, runs on your device.Open

Way 2: several pages on 1 sheet, all inside getPDF

If 1 image is what you need, and tall is not essential, Pages per sheet does the stacking for you. It places 2, 4, 6 or 9 pages on 1 sheet of A4, Letter, Legal, A3 or A5 as sharp vector copies, so the text stays text until you convert.

1. Drop the PDF on Pages per sheet and pick the number under Layout. Leave Gap at 5 mm, or set 0 for no space.
2. Press Lay out and download the new PDF.
3. Convert page 1 of it with PDF to JPG at 300 dpi, so each small page keeps enough pixels.

What came out of our 4-page test invoice and a 2-slide deck:

Input	Pages per sheet	Image at 300 dpi
4 A4 pages	4, on A4	1 portrait image, 2480 x 3508 px, 624 KB, 2 rows of 2
4 A4 pages	2, on A4	landscape sheets, 3508 x 2480 px, 2 pages side by side
2 slides (16:9)	2, on A4	1 portrait image, the slides one above the other

The tool picks the arrangement that gives each page the most room, so portrait pages go side by side and wide slides stack top to bottom. With 4 pages per sheet, each page ends up a little over 1100 pixels wide in the image: readable when you zoom, small at a glance.

Pages per sheet2, 4, 6 or 9 pages on 1 sheet, text kept sharp. Free, runs on your device.Open

The honest part: when to send the PDF instead

Past roughly 5 pages, a long image stops being convenient. It gets heavy, the app shrinks it until the text is mush, and the reader scrolls a thin strip with no page numbers and no search. A PDF opens in every phone’s built-in viewer, zooms without losing sharpness, and keeps the text searchable. In WhatsApp, attach it as a document and it arrives untouched (up to 2 GB).

If the long image is going to Instagram, it does not fit at all: Instagram keeps shapes between 1.91:1 and 3:4 and crops anything taller, so a 1 : 4 strip loses most of itself. Post the pages as a carousel instead; the Instagram guide shows the crop that fits.

PDF to JPG has no stitch option today. The 2 ways above are the real ones, and we would rather say so than pretend. For converting only some pages, see converting specific pages, and for the formats and resolutions in general, PDF to images.