Nothing is uploaded. When you drop or pick a PDF, the tool reads it locally with the browser’s File API, renders its pages in memory with the pdf.js engine (whose worker is bundled locally, not fetched from a CDN) and rebuilds the compressed file with the pdf-lib library on your own machine. There is no server, upload, database, API or tracking in the processing path, so certificates, ID scans, mark sheets and private paperwork you are shrinking for a form stay on your device; the tool works offline once cached, and closing the tab discards everything. The only optional network use anywhere on the site is consent-gated advertising, which never sees your files.

It depends on what is inside the PDF, but 150 KB is a comparatively comfortable target. The real savings come from re-encoding images, so a text-only or lightly formatted document falls well under 150 KB, and a typical single-page certificate or mark-sheet scan reaches it with legibility to spare. A long multi-page scan or a file full of photographs still has a floor: past a certain point the pages would turn to mush, so the tool stops at the smallest readable size it can reach and reports that figure with a note rather than producing an unusable file. If you are stuck above 150 KB, enabling grayscale, removing pages you do not need, or splitting the document first will usually get you under the cap. The three variants let you take the Smallest one when you need every byte, or Best Quality when 150 KB is comfortably met.

To reach a 150 KB target the tool leans on lossy compression — it down-samples the page images to a lower DPI and re-encodes them as JPEG, which is how a large file becomes small. That trades some sharpness for size, but 150 KB leaves more room than 50 KB or 100 KB, so scans usually stay noticeably crisper. Three variants are generated in one pass (Best Quality, Balanced and Smallest) and the tool defaults to the best one that still fits. One honest note: when whole pages are rasterised to hit the target, the text on those pages becomes part of the image and is no longer selectable or searchable; if you need the text to stay live, choose a larger target or a lossless PDF tool. For most single-page scans and certificates headed to an upload form, the 150 KB result stays perfectly legible.

Some government recruitment and examination portals cap uploaded documents at 150 KB, and many others cap at 200 KB — where guidance suggests aiming a bit under the limit for a safety margin, so a 150 KB file gives roughly 25% of headroom and avoids last-minute rejections. Compared with a 100 KB or 50 KB target, 150 KB lets the tool compress more gently, so scanned certificates and mark sheets keep more of their detail while still clearing the cap. This tool is built for exactly that: the target is fixed at 150 KB so you can drop the PDF and download a version that clears the limit, without hunting through compression settings. If the portal wants a smaller file, sibling tools target 100 KB and 50 KB, and larger presets (200 KB and up) exist for looser limits.