Does compressing a PDF reduce its quality?

It depends on the mode. Preserve mode re-encodes embedded images at a lower JPEG quality but keeps selectable text, links, bookmarks, and form fields intact. You may notice slight softening on high-resolution photos, but text rendering is unchanged. Aggressive mode rasterises every page to a JPEG image, which removes selectable text and structural elements entirely — visual quality depends on the preset you choose (Smallest file, Balanced, or Best quality).

Can I still select and copy text after compressing?

In Preserve mode, yes — selectable text survives compression. In Aggressive mode, no. Aggressive flattens each page to a raster image, so text is no longer selectable, searchable, or copy-able. If you need to keep text accessible, use Preserve.

Why did Preserve mode barely reduce my file size?

Text-heavy PDFs are usually already well compressed by their authoring tool. Preserve mode works by re-encoding embedded images at a lower quality. If your PDF contains mostly text and vector graphics with few or no raster images, there is little for Preserve to optimise. The result panel will tell you when this happens. Switching to Aggressive will shrink the file further by re-rendering pages as images, but you lose selectable text.

What happens to fillable form fields?

Preserve mode refuses to compress PDFs that contain fillable form fields (AcroForms) rather than risk corrupting them silently. You will see a message explaining the refusal. Aggressive mode will process these PDFs, but it flattens form fields to images — they will no longer be fillable. If you need to keep form fields functional, keep the original file.

Is there a file size limit?

The tool processes files in your browser's memory. Practical limits depend on your device — most modern laptops and desktops handle PDFs up to several hundred megabytes without issues. Phones and tablets with less available memory may struggle with very large files. Free-tier batch limits apply to the number of files per session; see the [pricing page](/pricing/) for details.

How to Compress a PDF (Free, No Upload)

Why compress a PDF

PDFs accumulate weight quickly. A scan of a ten-page document can easily reach 30 MB when each page is a high-resolution image. Reports exported from design tools embed full-resolution graphics. Slide decks converted to PDF carry every image at its original size.

Large PDFs cause friction: email attachment limits bounce them, cloud storage fills up faster, and page-load times slow down when the PDF is hosted on a website. Compression removes that friction by reducing the file size while keeping the document usable.

Two modes: Preserve and Aggressive

The PDF Compressor offers two distinct compression strategies. They are not just quality levels — they work differently under the hood, and the tradeoffs matter.

Preserve mode (default)

Preserve mode re-encodes the raster images embedded in the PDF at a lower JPEG quality. Everything else — selectable text, links, bookmarks, form fields, vector graphics — stays intact. The document structure is unchanged; only the image data gets smaller.

This is the right choice for invoices, reports, contracts, e-books, and any PDF where you need to copy text, click links, or fill in form fields after compression.

The tradeoff: if your PDF is mostly text and vector art with few embedded images, Preserve mode may not reduce the file size meaningfully. The tool will tell you when this happens.

One important limitation: Preserve mode refuses to process PDFs with fillable form fields (AcroForms). Rather than risk silently corrupting interactive fields, the tool blocks the operation and explains why. If you need to compress a PDF with form fields, you can use Aggressive mode — but the fields will be flattened to images and will no longer be fillable.

Aggressive mode

Aggressive mode renders every page of the PDF to a JPEG image at a resolution and quality level you choose, then assembles those images into a new PDF. The output is a flat image-based document.

This produces the largest file-size reduction, especially on scanned documents and photo-heavy PDFs that are already image-based. For a typical scan, Aggressive mode can cut file size by 50% or more depending on the quality preset.

The tradeoff is real: Aggressive mode removes selectable text, links, bookmarks, and form fields. The output cannot be made searchable again without running OCR on it (which this tool does not do). Always keep your original if you may need the text later.

Aggressive mode offers three quality presets:

Smallest file — maximum compression, lower visual quality. Good for archival copies you rarely view at full zoom.
Balanced — a middle ground between size and clarity.
Best quality — lighter compression, sharper images. Good for documents you still need to read on screen.

Step-by-step: compress a PDF

1. Open the PDF Compressor.

2. Drop one or more PDF files onto the upload area, or click to browse. You can also paste a PDF from your clipboard.

3. Choose Preserve (the default) or Aggressive. If you pick Aggressive, an inline warning reminds you that selectable text will be removed.

4. If you chose Aggressive, pick a quality preset: Smallest file, Balanced, or Best quality.

5. Click Compress. The tool processes each file in your browser — nothing is uploaded to a server.

6. Review the results. Each file shows its original size, compressed size, and the percentage reduction.

7. Download individual files or, if you compressed multiple PDFs, download them all as a single ZIP.

What to expect from file sizes

Compression results vary widely depending on the content of the PDF:

Scanned documents (image-based PDFs): Preserve mode re-encodes the page images and typically reduces size by 20–40%. Aggressive mode can reduce size by 50–70% or more.
Text-heavy reports and contracts: Preserve mode may produce little to no reduction, because the text is already compact. Aggressive mode will still shrink these files, but at the cost of losing selectable text.
Design-heavy PDFs (marketing collateral, slide exports): Preserve mode can produce significant savings if the document embeds large raster images. Results depend on how the PDF was originally exported.

If Preserve mode reports minimal savings on a text-heavy PDF and you need a smaller file, consider whether losing selectable text is acceptable before switching to Aggressive.

Browser limits

All processing happens in your browser using JavaScript. The PDF never leaves your device, which is the privacy advantage — but it also means the tool runs within your browser's memory constraints.

Most modern desktop browsers can handle PDFs well into the hundreds of megabytes. Mobile browsers have tighter memory limits and may struggle with large files or batch compression of many files at once. If the browser tab crashes or goes unresponsive, try compressing fewer files per batch or use a desktop browser.

Free-tier users have batch and file-size limits. See the pricing page for current thresholds.

When to use each mode

| Scenario | Recommended mode |

|----------|-----------------|

| Emailing an invoice or contract | Preserve |

| Shrinking a scan for archival | Aggressive (Balanced or Smallest) |

| Reducing a slide deck export | Preserve first; Aggressive if savings are insufficient |

| Compressing a photo album PDF | Aggressive (Best quality) |

| PDF with fillable form fields | Keep original — Preserve refuses, Aggressive flattens fields |

Related guides

How to Extract Pages from a PDF — pull specific pages into a new file.
How to Remove Pages from a PDF — delete unwanted pages and keep the rest.