Keeping image quality when you add it to a PDF
Last updated: 2026-07-27
An image looks fine on screen, goes into a PDF, and comes out of the printer soft and mushy. Nine times out of ten the PDF tool is not the culprit. The problem is the relationship between how many pixels the image has and how large it is printed — and once that clicks, you can predict the outcome before you place anything.
Resolution alone tells you nothing
The common instinct is that a big pixel count means sharp and a small one means blurry. What actually matters is how many pixels land inside one inch of the finished output: pixels per inch, usually called DPI.
Take a single image that is 300 pixels wide.
- Shrink it into a 1-inch-wide signature box: 300 pixels across one inch is 300 DPI. Print-quality, no complaints.
- Stretch the same file across 4 inches: 75 pixels per inch, or 75 DPI. Visibly soft, with jagged edges on any text.
The file did not change. Only the placement size did. This is why the exact same logo is crisp in one document and terrible in another, and why asking whether an image is high enough resolution is not answerable without knowing how big it will be printed.
The number to aim for
For print, 300 DPI at final size is the long-standing standard. For a document only ever read on screen, 150 DPI is usually acceptable, though high-density displays and readers who zoom in argue for more headroom. The arithmetic is one line:
Pixels needed across = final printed width in inches x 300
A logo placed 2 inches wide needs at least 600 pixels across; a photo spanning 6 inches needs 1800. You can read an image's pixel dimensions from file properties on Windows or Get Info on macOS — check that number before you place it, not after you print.
PDF measurements: points
Internally, PDF positions everything in points, and there are exactly 72 points to an inch. US Letter is 612 x 792 points; A4 is 595 x 842 points.
That conversion is genuinely useful. An image across roughly a third of an A4 page is about 198 points, or 2.75 inches, so 300 DPI requires an original around 825 pixels wide. It also exposes a trap: because a point is 1/72 inch, placing an image so its size in points equals its size in pixels puts it at exactly 72 DPI — a quarter of print resolution, and a default that looks perfectly plausible on a monitor.
Upscaling never adds detail
Enlarging a small image does not create new information — it invents intermediate pixels by averaging the ones that already exist. Take a 200-pixel image up to 800 pixels and the file now contains 800 pixels, but none of the added ones represent anything that was actually photographed or drawn. The result is smoother and larger, and no sharper. Detail absent from the original data cannot be recovered, no matter how the resampling is done.
So pre-enlarging an image before adding it to a PDF accomplishes nothing except a bigger file. The only real answer is to start from the largest original you can obtain: the brand asset file rather than the small version you right-click-saved off a web page, the camera original rather than the copy a messaging app sent you.
Every JPG re-save costs you something
JPG is lossy compression. To make the file small it permanently discards detail it judges your eye will not miss. The important part is that the loss compounds. Open a JPG, crop it slightly, save as JPG again, and the second compression is applied to already-damaged data. Repeat that a few times and you get visible blocky artefacts and ringing halos, especially around hard edges — which means scanned documents, screenshots and anything with text suffer far worse than photographs of landscapes.
Practical rules that follow:
- If an image needs several rounds of editing, keep the working copies as PNG. PNG is lossless, so re-saving costs nothing.
- A file that has already been through several JPG generations cannot be repaired. Fetch a fresh original instead.
- Messaging apps and social platforms usually recompress and downscale on send. When quality matters, ask for the file by email or a file-sharing link.
- Screenshots are typically captured as PNG. Leave them that way rather than converting to JPG.
The check, in short
Decide how wide the image will be on paper. Multiply the inches by 300. Compare to the pixel width of your original. If it falls short, your options are to place it smaller or to find a better source — there is no third option.
The same applies when placing images in StickPDF. Every time you drag the corner handle outward, the effective DPI drops proportionally, so if the image needs to be large on the page, start with a file that has the pixels to support it. Scaling down is always safe: the full original image data goes into the exported PDF, and transparency in a PNG is preserved.