Why Compress a PDF?
PDF files can become unexpectedly large — a single scanned document can exceed 10MB, a photo portfolio can reach 50MB. These sizes create real problems: email services like Gmail reject attachments over 25MB, university portals enforce 2–5MB upload limits, and WhatsApp compresses shared PDFs in ways that degrade formatting. Compressing a PDF solves all these problems while keeping the document fully readable.
What Affects PDF File Size?
Understanding what makes a PDF large helps you choose the right compression approach:
- Embedded images: The biggest contributor. High-resolution photos at 300+ DPI can make a PDF enormous. Downsampling to 96–150 DPI is usually invisible on screen.
- Scanned pages: Each scanned page is stored as a raster image. Running OCR converts these to text, which compresses far more efficiently.
- Embedded fonts: Full font embedding includes every character in the font. Subsetting keeps only the characters actually used in the document.
- Duplicate objects: Older or converted PDFs often contain redundant embedded resources that can be safely stripped.
How to Compress a PDF on Mac Without Losing Quality
On macOS, you can compress a PDF through Preview's "Export as PDF" with Quartz filter — but the results are often poor and unpredictable. For reliable, high-quality compression on Mac:
- Open heyPDF's Compress PDF tool in Safari or Chrome.
- Drag your PDF from Finder into the browser window.
- Select your compression level (Standard keeps quality high; Maximum achieves smallest file size).
- Click Compress and download your result.
How to Compress a PDF on Windows
Windows has no built-in PDF compressor. The simplest method: open heyPDF in Chrome or Edge, upload your PDF (drag from File Explorer or Browse), select compression strength, and download. The process takes under 30 seconds for most files.
How Much Can a PDF Be Compressed?
Typical compression results on heyPDF:
- Scanned documents (JPEG-heavy): 60–85% size reduction
- Mixed content (Word exports, presentations): 30–60% reduction
- Text-only PDFs (invoices, reports): 10–25% reduction
A 5MB scanned form can typically be reduced to under 500KB, and a 20MB photo portfolio can often be brought to 3–5MB.
How to use Compress PDF — step by step
Open Compress PDF
Visit heyPDF's Compress PDF tool — no account or software needed.
Upload Your PDF
Drag your PDF into the upload zone or click to browse. You can also import from Google Drive or Dropbox.
Choose Compression Level
Select Standard for minimal quality loss, High for a smaller file, or Maximum to hit strict size targets like 100KB or 200KB.
Download Compressed PDF
The new file size is shown before you download. Your file is deleted from our servers automatically after 2 hours.
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Frequently Asked Questions
Yes, at Standard and High compression levels, text and document structure remain fully crisp. Only embedded images are reduced in resolution — and at 96–150 DPI, the difference is typically invisible on screen and acceptable for most printing.
Use the High or Maximum compression setting on heyPDF's Compress PDF tool. For most PDFs, Maximum compression achieves files under 500KB. If you need even smaller results, use Split PDF to remove unnecessary pages before compressing.
Very small text-only PDFs don't compress much because they're already efficient. If your PDF contains many high-resolution photos, try Maximum compression. If it's a scanned document, run it through OCR first — text-based PDFs compress significantly better.
No. Compression only removes redundant data and reduces image resolution — it never corrupts the document structure. The output PDF remains valid and fully compatible with all PDF readers.
Open Safari on your iPhone, go to heypdf.vercel.app, tap Compress PDF, then tap 'Select Files' to choose from your Files app or iCloud Drive. The compressed PDF will download directly to your device.
Related PDF Tools
After using Compress PDF, you might also need these tools:
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Expert Resources
How to Compress PDF Without Losing Quality — 5 Methods
Reduce file sizes up to 90% while keeping all vector layouts, fonts, and images crystal clear.
How to Make PDF Smaller — Reduce File Size Guide
Explore the best methods to shrink heavy files for email attachments, university submissions, and websites.