VUISO COMPRESS PDF - how to use =============================== Make a PDF small enough to upload or e-mail, and look at every page before you save it. Everything happens inside your browser. Nothing is uploaded, there is no account, and it works with the network switched off. This tool works on ONE FILE at a time. To combine several use Vuiso Merge PDF; to drop pages use Vuiso Split PDF. OPENING IT Double-click "Vuiso Compress PDF.html". It opens in your browser like a normal page. There is nothing to install. Chrome or Edge is recommended; Firefox and Safari work too. THE SHORT VERSION 1. Open PDF (or drag the file onto the page area) 2. Compress Balanced is set to start with 3. Save PDF Nothing is written until you press the button in the Save window, and Save only becomes available once there is a smaller copy to save. HOW SMALL: TWO WAYS TO SAY IT Pick a level Light, Balanced or Strong, or set the two sliders yourself. Resolution how many dots per inch pictures keep. 150 dpi reads well on any screen. Use 200 or more if the file will be printed. Picture quality how much detail the JPEG encoder keeps. Below about 40% edges start to smudge. Size limit Type the largest size the file may be, or pick 200 KB, 500 KB, 1 MB or 2 MB: the limits upload forms usually ask for. The tool tries settings from sharpest to smallest and keeps the SHARPEST one that still fits. It does not guess: each try is a real compression of your file, measured. A limit is counted in thousands of bytes (500 KB = 500,000 bytes), which is the stricter of the two ways an upload form can count. A file that fits shows a number at or under your limit in Windows Explorer too. TWO METHODS Keep text The document itself is kept. Pictures inside it are made smaller and saved again as JPEG; text, fonts, links, bookmarks and form fields are left exactly as they were, so the text can still be selected and searched. This suits almost every file, scans included, because a scan is already a picture of a page. Along the way it also drops leftovers nothing points at any more (old copies of edited pages, for instance) and compresses any part the original stored uncompressed. Pages as pictures Every page is drawn as one JPEG and the file is rebuilt from those pictures. This goes furthest, especially on drawings and files full of vector graphics, but: - text can no longer be selected or searched - links, bookmarks and form fields are gone Use it when Keep text cannot get under your limit. WHAT KEEP TEXT LEAVES ALONE, AND WHY A picture is only changed when the tool understands it completely. Anything else is copied across untouched, because skipping costs a few kilobytes and guessing wrong would cost your document. Left alone: - CMYK pictures, and the rarer colour models (Indexed, Lab, spot colours) - JPEG 2000, JBIG2 and fax-compressed pictures - transparency masks (JPEG would put halos round the edges) - pictures that come out barely smaller as JPEG than they already are A file made mostly of these may not get much smaller with Keep text. The result says so, and Pages as pictures is the way forward. One more honest detail: a picture is never given more resolution than the largest page in the file could show at the dpi you chose. A picture printed small on its page may keep more pixels than it strictly needs. That errs on the side of sharpness. THE RESULT After a run, the size before and after sits above the pages, with how much smaller the file became and what was done. With a size limit it also says whether the limit was met. If even the smallest setting does not fit, you get that smallest copy anyway, clearly marked, and a suggestion. If the copy would not be at least 1% smaller than the original, there is nothing to save and the tool says so instead. Changing any setting throws the copy away. What Save writes is always what the settings on screen made. CHECK IT BEFORE YOU SEND IT Original / Compressed switches every page in the grid between the two. Click a page opens it large. Zoom in doubles it. Space flips between Original and Compressed, in the grid or in the large view: the fastest way to see whether small print survived. Left / Right previous and next page in the large view. Esc closes the large view. SAVING "Save PDF" shows a summary first: the source file, both sizes, the method and the output name. Nothing is written until you press the button in that window. The copy is named " - compressed.pdf". Your original file is never modified. KEYBOARD SHORTCUTS Ctrl+O Open PDF Ctrl+Enter Compress Ctrl+E Save PDF Space Original / Compressed Esc Close the large view NOTES - Password-protected PDFs cannot be opened. Remove the protection in the program you use to open the document, save an unprotected copy, and use that. - How long it takes depends on the number of pictures and pages. A size limit runs the compression several times (usually three to five) to find the sharpest setting that fits. The Stop button ends a run at once and changes nothing. - Memory, as a rough guide: allow about 300MB plus several times the size of the file. Pages as pictures at a high resolution needs the most. If the browser ever runs out it closes the tab, and because your original is never written to, nothing is lost but the settings. - Nothing is stored. No cookies, no database. The only thing remembered is which of the two languages you chose. PRIVACY The file contains a Content-Security-Policy that forbids network connections entirely. That is enforced by the browser, not promised by us: open DevTools, watch the Network tab, and it stays empty. You can also disconnect from the internet and the tool still works. Verify the copy you hold matches the one published: Windows Get-FileHash "Vuiso Compress PDF.html" -Algorithm SHA256 macOS/Linux shasum -a 256 "Vuiso Compress PDF.html" Compare the result with the SHA-256 printed on the download page and in the .sha256.txt file next to this one. LICENCE See LICENSES.txt, which must stay alongside the tool.