Compress PDF Online
Upload a PDF and Ghostscript rebuilds it with the embedded images downsampled and re-encoded, so scans and photo-heavy reports lose the most weight. Text stays vector and selectable, but fillable form fields are dropped from the compressed copy.
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What Compressing a PDF Actually Changes
A PDF that is too big for an email attachment or a portal upload is almost always carrying raster images: scanned pages, phone photos of documents, screenshots pasted into a report, or print-resolution product shots. The text layer of a normal document is a few kilobytes of vector instructions, while a single 300 ppi color scan of one A4 page can be several megabytes on its own.
MiConvert runs the file through Ghostscript's pdfwrite device at one of three presets and writes a new PDF 1.4 file. Maximum (smallest file) downsamples images to 72 ppi, Balanced downsamples to 150 ppi, and Quality targets 300 ppi, which usually leaves a 300 ppi scan untouched. On a 2400x1800 pixel page we measured 1.59 MB dropping to about 81 KB at the Balanced setting and about 26 KB at Maximum. The upload is processed on our servers, not in your browser, and Ghostscript gets 180 seconds per file, so a very large book scan can hit that limit and fail.
What survives: text stays real text you can select and search, bookmarks and the outline tree stay intact, link annotations keep working, and the document Title is preserved. What does not: an AcroForm is removed, so a fillable form comes back as flat static content showing whatever values were in it. At the Maximum setting the standard fonts are left unembedded, which is fine for screen reading but can shift layout on a printer that substitutes a different Helvetica. Nothing here is lossless, and any existing cryptographic signature on the input is invalidated because the whole file is rewritten.
This page exists for people hitting a hard size cap: a 10 MB email limit, a court or tax portal that refuses anything over 5 MB, a CMS upload field, or an archive where a thousand scanned invoices cost more in storage than they are worth.
How to Compress a PDF Here
- 1
Check that the PDF opens without being asked for a password. Open-password files are rejected before compression and this page shows the raw code ERROR_PDF_PASSWORD_PROTECTED; run them through our PDF password-removal tool with the password first. A PDF that only has permissions restrictions and opens normally is fine.
- 2
If the document is a fillable form you still need to fill, keep the original somewhere safe. The compressed copy keeps the look of the fields but not their interactivity.
- 3
Drop in your PDF, or several of them: up to 10 files per run without an account, 25 on Plus and 50 on Pro, with a per-file ceiling of 50 MB as a guest, 100 MB with a free account, 200 MB on Plus and 1 GB on Pro.
- 4
Pick a level. Balanced (150 ppi) is the default and is the right first try for scans you only need to read on screen. Choose Maximum when a hard attachment limit matters more than image detail, and Quality when the file will be printed.
- 5
Compare the before and after sizes shown after the job finishes. If the saving is not enough, run the original again one level lower rather than compressing the compressed file, which just re-encodes already-degraded images.
What This Tool Does
- Three Ghostscript presets with known behavior: 72 ppi, 150 ppi, or a 300 ppi target for images, applied to every raster image in the file
- Keeps text as selectable vector text, so search and copy still work after compression - no rasterizing of pages
- Keeps bookmarks, clickable links and the document Title; the outline tree still navigates the compressed file
- Shows the original size, the new size and the percentage saved as soon as the job finishes
- If Ghostscript's output is not smaller than the input, the original file is returned unchanged rather than a larger one
- Handles PDFs that carry only an owner or permissions password without needing that password
Questions People Ask About Compressing PDFs
Can I compress a PDF to exactly 100 KB, 200 KB or 1 MB? ▼
No. There is no target-size field; you pick an image resolution preset and get whatever that produces for your document. If a portal demands under 1 MB, try Balanced, check the reported size, then rerun the original at Maximum. For a long scanned file that still will not fit, split it into parts with our Split PDF tool and send them separately.
Will compression reduce quality? ▼
For images, yes, and that is where the savings come from. Photos and scans are downsampled to 72 or 150 ppi and re-encoded as JPEG, which softens fine detail and can blur small text that was captured as part of a scan. Text that is real text in the PDF is untouched and stays sharp at any zoom level.
My file came back the same size. What happened? ▼
A text-only PDF usually has nothing left to squeeze, and at the Quality preset an image already at or below 300 ppi is passed through. When the rebuilt file would be larger than the original, we return the original unchanged and still mark the job as successful.
Does the compressed file keep my fillable form fields? ▼
No. Ghostscript's rewrite drops the AcroForm, so checkboxes and text fields stop being fillable and whatever was typed in them is drawn into the page as static content. Compress a copy and keep the fillable original if you still need people to fill it in.
The page shows ERROR_PDF_PASSWORD_PROTECTED. What do I do? ▼
That raw code means the PDF needs a password just to open, and we cannot read it. Remove the password first with our PDF password-removal tool, then compress the decrypted copy. PDFs that open freely but restrict printing or copying pass straight through the compressor.
Will my scanned PDF become searchable after compressing? ▼
No. There is no OCR anywhere in this tool. A scan is a picture of a page before compression and a smaller picture of a page afterward. If you need searchable text you need an OCR step elsewhere first, then compress the result.
Is this the same as converting PDF to PDF/A, or merging PDFs? ▼
No. The output here is a plain PDF 1.4 file with no PDF/A conformance, and existing PDF/A status does not survive the rewrite - use our PDF to PDF/A converter for archival files. Combining several documents into one is a separate job; our Merge PDF tool joins them in upload order.
What happens to my file after I download it? ▼
The PDF is uploaded to our servers for processing, not handled in your browser. The uploaded original is removed by a cleanup sweep once it is more than two hours old, and the compressed output plus its download link stay available for roughly four hours before being deleted automatically. The link is a random token, but anyone who has it can download the file until it expires, so do not share it. File names, sizes and outcomes are logged for operations.
