How to compress a PDF on this page
- Add one PDF. Drop it on the box or click to browse. The row that appears confirms the file name, its current size and its page count.
- Choose a quality. The slider has three stops: Smallest, Balanced and High quality. Balanced is the starting point, and the line underneath explains what each one is for.
- Compress. The progress label counts through the pages so you can see how far along a long document is.
- Check the numbers, then download. The result line shows the old size, the new size and the percentage saved, so you decide before anything reaches your downloads folder.
Every page is processed; there is no page selection. The work happens inside this page on your own device, so the document is never uploaded to a server.
Exactly what this tool does to your file
It is worth being precise, because "compress" means different things in different programs. This tool redraws every page and saves it as a JPEG photograph of itself, then builds a new PDF where each page holds nothing but that one image.
Two settings do the work. The first is the width each page is drawn at: roughly 1000 pixels on Smallest, 1400 on Balanced and 2000 on High quality. On a Letter or A4 page that works out at about 120, 165 and 235 dots per inch. The second is how hard the JPEG encoder squeezes what it drew, from firm on Smallest to gentle on High quality. Pages narrower than the target are not blown up more than two and a half times, so a small page cannot balloon.
The new page keeps the original page's exact dimensions in PDF points, so the document still prints at its proper paper size. What it does not keep is everything that was not a picture. Selectable text, vector logos, links, highlights, comments and interactive form fields all become flat pixels in a photograph of the page. That trade is the whole reason the savings can be so large, and it is permanent: compression throws data away and cannot be undone, so keep your original and save the compressed copy under a different name.
What shrinks well, and what does not
The single question that predicts your result is whether the file is made of pictures or made of text.
- Scans shrink hugely. A scanner saves a photograph of each page, often at 600 dots per inch in full color. Redrawing that at 165 dots per inch throws out most of the data while staying comfortably readable on screen. Scanned and image-heavy PDFs routinely shrink by 70-90%.
- Photo-heavy exports shrink well. Slide decks and reports that embed full-resolution phone photos carry far more pixels than the page ever displays.
- Text-only PDFs barely move, or grow. A document exported from a word processor stores letters as fonts and vector outlines, which is already about as small as it gets. Turning that into a photograph can easily produce a larger file.
- Already-modest scans can grow too. If a page was scanned at 100 dots per inch and you ask for 165, the tool is adding pixels rather than removing them.
When the result is not smaller, the tool says so in plain words instead of handing you a worse file, and you can simply not download it. Dropping to Smallest is the next thing to try. For the full account of what makes documents balloon in the first place, and the fixes that happen before compression, read why is my PDF so large.
Setting realistic expectations
Pick the lowest setting that still looks right to you rather than the lowest available. Smallest is aimed at hitting a hard upload limit; Balanced keeps scanned text crisp enough for everyday email; High quality is for documents someone will actually read closely or print. Open the download and look at it before you delete anything, especially if the pages carry fine print, small figures or handwriting.
Order of operations matters as well. If you only need part of a long document, extract those pages first and compress the short version. If you are combining files, merge them all and compress once at the end rather than compressing each piece beforehand, because compressing twice throws data away twice.
If you need the text to stay real text at a smaller size, this is the wrong instrument. The "reduce file size" or "optimize" export in your own PDF application works differently and can leave the text layer intact.
One practical note for long documents: pages are drawn and encoded one at a time, so a several hundred page file takes a while and asks a lot of a phone's memory. The progress label counts the pages, and dropping to a lower quality setting makes the whole job lighter as well as faster.
Frequently asked questions
How much smaller will my PDF actually get?
It depends entirely on what is inside it. Scanned and image-heavy documents routinely drop 70-90% at the Balanced setting, while a text PDF exported from a word processor may not shrink at all. You never have to guess: the tool shows the old size, the new size and the saving before you download anything.
Will my text still be selectable and searchable afterward?
No. Every page is redrawn and saved as a single JPEG image, so text becomes part of the picture and can no longer be selected, searched or copied. Keep your original if you need those, or use the reduce file size export in your own PDF application instead.
What do the three quality settings change?
Two things: the width each page is drawn at, roughly 1000, 1400 or 2000 pixels, and how hard the JPEG encoder squeezes the result. On a Letter or A4 page those widths are about 120, 165 and 235 dots per inch.
My PDF came out the same size or bigger. What went wrong?
Nothing. There was simply nothing image-heavy to squeeze, or the pictures inside were already lower resolution than the setting draws at, so pixels were being added rather than removed. Try the Smallest setting, or leave the file as it is.
Related tools: Split PDF to send only the pages that matter, Merge PDF to combine documents first, and PDF to JPG when you want the pages as images rather than as a document.