You turn a PDF into images to drop a page into a slide, to publish just the diagram, to show the contents to someone who cannot open PDFs, or to submit artwork to a printer. Those uses need wildly different resolutions, yet most converters never ask — and hand you something either unusably coarse or needlessly enormous.
OFFiler makes resolution an explicit choice. Every page is written out as a PNG, entirely inside your browser. Below: what that DPI number actually controls, why the output is PNG, and what to do with the images afterwards.
What happens inside
DPI is pixel density against the page's real size
PDF's coordinate system uses 1/72 inch as its unit, which means a PDF genuinely knows that a page is A4-sized. The DPI you pick decides how many pixels are drawn per inch of that physical size; internally the tool divides your DPI by 72 and uses the result as a render scale. At 150 dpi an A4 page comes out around 1240×1754 pixels; at 300 dpi, around 2480×3508.
The choices are 72, 96, 150, and 300 dpi, defaulting to 150. Pick 96–150 for on-screen use, 150–300 if the image may be enlarged inside a document, and 300 for print. Pixel count grows with the square of the number, so 300 dpi weighs roughly four times what 150 dpi does.
Rendered the way a viewer shows it
Rendering goes through PDF.js using the same display intent a PDF viewer uses. Switching to print intent can leave screen-only content blank on some PDFs, so the display path is used deliberately. The canvas is filled white before drawing, so transparent regions never come out black.
Decoders for JPEG 2000 and JBIG2 images — common in scanner output — are bundled with the site rather than fetched from a CDN, so those PDFs can be rasterised offline too.
Output format and limits
Output is always PNG — chain a converter for JPEG
Images are written as PNG. PNG is lossless, so what was rendered is what gets saved, with none of the fringing JPEG puts around glyph edges — which is what matters most on pages made of text and diagrams.
On pages dominated by photographs, however, PNG is substantially larger than JPEG would be. If size matters more, pass the output to format conversion for JPEG or WebP, or to image compression to dial in a quality level. Both accept the result directly.
Every page is rendered, and heavy PDFs take time
Conversion covers the whole document. Rendering a long PDF at 300 dpi will use a meaningful amount of memory and time. If you only need certain pages, extract them first and convert the smaller file. Password-protected PDFs cannot be opened.
Chaining around the conversion
Sharing part of a document safely
When only part of an internal document should leave the building, handing over the PDF also hands over selectable text and document metadata. Extract the pages, convert them to images, then paint over what must be hidden with image markup — and what you send is exactly what is visible.
Note the order matters: markup paints on top. Once the page is an image, the pixels underneath really are covered; redacting while it is still a PDF leaves the text layer in place.
Specs and limits
- Input format
- PDF (application/pdf)
- Size limit
- 100 MB per file
- Output format
- PNG (lossless)
- Resolution
- 72 / 96 / 150 / 300 dpi (default 150)
- A4 pixel size
- ≈1240×1754 at 150 dpi, ≈2480×3508 at 300 dpi
- Pages
- All pages — extract first if you need a subset
- Background
- Filled white before drawing; transparency never turns black
- Network
- No upload; decoders bundled, works offline