Why does my exported page look blurry when I zoom in?

Because it was rendered at too low a resolution for the size you are viewing it at. An exported image is a fixed grid of pixels — enlarging it magnifies those pixels rather than revealing detail. Re-export at a higher DPI.

Does exporting at 600 DPI give me a better result than 300?

Only if something will actually use that detail. Beyond the resolution your screen or printer can reproduce, extra DPI adds file size and rendering time and nothing visible. 300 DPI covers almost all printing; 150 is generous for screen use.

Guide

PNG or JPEG? Choosing a Format and DPI When Exporting PDF Pages

Exporting a PDF page as an image asks you two questions before it will do anything: which format, and what resolution. Both defaults are usually fine, which is why most people never think about them — and then one day the exported page comes out blurry, or enormous, or with fuzzy grey halos around the text, and the settings suddenly matter.

The one rule that decides the format

Text and line art: PNG. Photographs: JPEG. Almost every case follows from that, and it follows from how the two formats compress.

PNG is lossless. It reconstructs your image exactly, pixel for pixel, and it compresses by finding repetition — which is abundant in a document page, where large areas are identical white and text is solid black. A page of text as PNG is both perfectly sharp and surprisingly small.

JPEG is lossy. It discards detail the eye is unlikely to miss, which works beautifully on photographs, where colours shift gradually and small errors disappear into the texture. On text it fails visibly: the hard black-to-white edge of a letter is precisely the kind of abrupt transition JPEG handles worst, producing faint grey smudging around characters. At small sizes it's a slight muddiness; on fine print it's genuinely hard to read.

So a scanned photograph exports well as JPEG at a fraction of PNG's size. A scanned contract exports as a crisp PNG that's often smaller than the JPEG would have been anyway. A page mixing both — a report with charts and a photo — should go to PNG, because unreadable text is a worse outcome than a larger file.

What DPI actually means here

DPI — dots per inch — describes how finely the page is sampled when it's drawn into a grid of pixels. A PDF page has a physical size, so DPI and pixel dimensions are two ways of saying the same thing. An A4 page is 8.27 inches wide, so:

72 DPI → about 595 pixels wide. Fine for a thumbnail, too coarse to read comfortably.
150 DPI → about 1,240 pixels. Comfortable on screen, readable, modest file size.
300 DPI → about 2,480 pixels. The standard for print; sharp when zoomed.
600 DPI → about 4,960 pixels. Rarely needed outside professional printing or archival work.

Note that doubling DPI quadruples the pixel count, because it doubles both width and height. Going from 150 to 300 makes the file roughly four times larger; 150 to 600, sixteen times. That's the whole reason the choice matters.

A ceiling worth knowing about

If your PDF is text-based, you can export at any resolution you like and it will be sharp — text is drawn from font outlines, so the renderer simply draws it larger. There's no upper limit on quality, only on usefulness.

If your PDF is a scan, there's a hard ceiling: the resolution it was scanned at. Exporting a 200 DPI scan at 600 DPI produces a file nine times the size containing exactly the same detail, enlarged. You cannot recover information that was never captured. Working out which kind of PDF you have tells you whether pushing the DPI up will achieve anything.

Picking settings by destination

Inserting into a slide or document: PNG at 150 DPI. Sharp on screen and when projected, without bloating the host file.
Printing: 300 DPI. PNG for documents, JPEG if the page is photographic.
Posting online or emailing: 150 DPI, JPEG for photos and PNG for anything with text.
Archiving a scan: PNG at the scan's native resolution. Lossless matters when it's the copy of record.
A quick visual reference: 72–100 DPI. Small and instant.

Exporting with HerePDF

The PDF to image tool offers 72, 150, and 300 DPI, chosen before you load the file since resolution determines how each page is rendered. Rendering happens in your browser via PDF.js — nothing is uploaded — so a long document at 300 DPI is real work for your device and will take a moment. Every page is exported separately, with individual downloads and a ZIP for the whole set.

One practical consequence of local rendering: very long documents at high DPI are limited by your device's memory. If a large file struggles, export at a lower resolution, or split out the pages you actually need first and convert those.

If you're unsure

Export one page at 150 DPI as PNG and look at it at the size you'll actually use. If it's sharp enough, you're done — and you have the smallest file that does the job. If it isn't, go to 300. That single test is faster than reasoning about it, and it beats defaulting to the highest setting and carrying files four times larger than you need.