Print resolution: dpi & ppi

dpi (dots per inch) or ppi (pixels per inch) says how many image pixels land on one inch of paper. For anything viewed up close – flyers, business cards, brochures, photos – 300 ppi is the standard. For large formats viewed from a distance, like posters or roll-up banners, 150 ppi is often enough.

What really counts: effective resolution

The number in your image properties doesn't matter. What matters is how many pixels the image has compared to the size it's placed at. A photo 3,000 pixels wide is enough for 10 inches at 300 ppi. Stretch it to 20 inches in your layout and it only has 150 ppi left. Formula: pixels = inches × dpi (or mm ÷ 25.4 × dpi).

Can I just increase the dpi?

No. Changing the dpi value in an image program without adding pixels changes nothing about the sharpness. And upscaling doesn't invent details either – it only makes the image bigger, not sharper. If an image is too small: use a better original or place it smaller.

PreflightPilot calculates the effective resolution of every image in your PDF from its actual placed size and marks images that are too low.