How to Compress a PDF: Reduce File Size Safely

Choose a compression level

Keep the original, and use Basic or no compression at all, when:

• people need to select, copy or search the text, or use a screen reader²;
• the PDF has form fields that still need filling in, or links that must stay clickable;
• it is a text document that is already small: turning its pages into images usually makes it bigger;
• it has been digitally signed: any compression rewrites the file, so the signature will no longer validate¹.

Does your PDF contain selectable text?

This decides which level is safe. Open the PDF in a PDF reader or your browser and try to select a word by dragging across it, or use Find (Ctrl+F, or Cmd+F on a Mac) to search for a word you can see on the page.

• You can select or find the word: the PDF contains real text, usually because it was exported from a word processor or spreadsheet. Basic keeps that text.
• You cannot: the page is most likely an image, such as a scan or a phone photo of paper². There is no text to lose, so Recommended or Maximum mainly affect how sharp the page looks.

What rasterizing means in practice. Recommended and Maximum “rasterize” each page: they draw it onto a canvas, like taking a screenshot, and store that picture as a JPEG. JPEG is a lossy format³ that discards fine detail to save space. The new file looks like the original, but its text is now pixels: you cannot select, copy or search it, links are no longer clickable although their text is still visible, form fields can no longer be edited (a value that was already typed stays visible in the picture), and bookmarks and document properties such as the title are not carried over.

Compress PDF does not add text back. If you need the words from a scanned page, ToolSolvo’s separate Image to Text (OCR) tool can read them so you can copy or download them, but it does not create a searchable PDF.

How to compress a PDF with ToolSolvo

1. Open the Compress PDF tool.
2. Drag your PDF onto the upload area or click Choose PDF file. The tool takes one file at a time, up to 200 MB. Password-protected PDFs must be unlocked first.
3. Under Compression level, choose Basic, Recommended or Maximum. Recommended is selected at first.
4. Click Compress PDF. With Recommended and Maximum, progress is shown page by page.
5. Read the result. If the file got smaller, you see “Your PDF is … smaller” with the sizes before and after, and a Download button. If it did not, the tool says “This PDF could not be made smaller at this level” and offers no download, because your original is already the smaller version.
6. To compare levels, click Try a different level. To start again with another file, click Compress another PDF.

Everything happens in your browser: the PDF is processed on your own device and is not uploaded to ToolSolvo or anyone else.

How to check the compressed file

• Size. The tool shows the size before and after, such as “3.3 MB → 456 KB”, and the percentage saved. It counts 1 KB as 1,024 bytes; your file manager may round or count slightly differently.
• Upload limit. Compare the new size with the limit of the form or email service you are using, not with the original.
• Readability. Open the downloaded file and zoom in on the smallest text, stamps and signatures. With Maximum, fine print can look soft.
• Text, links and forms. If you used Basic, try selecting a word, clicking a link and editing a field. If you used Recommended or Maximum, expect none of these to work.
• Pages. Check that every page is there and the right way up.

Keep your original until you are sure the smaller copy is good enough.

Why some PDFs shrink more than others

A PDF can contain three kinds of content, and they take up very different amounts of space:

• Text and vector graphics. Words are stored as characters plus the fonts needed to draw them, and shapes as drawing instructions. This is compact: a page of text often takes only a few kilobytes.
• Images. Photos, scans and screenshots are stored as grids of pixels, often JPEG-compressed (the PDF standard calls this the DCTDecode filter¹). A single high-resolution photo can be several megabytes, so images usually account for most of a large file.
• Leftovers from editing. Some programs save changes by appending them to the end of the file (an “incremental update”¹), so older copies of edited parts can stay inside the file.

Basic saves space by storing the file’s structure more compactly (compressed object streams, introduced in PDF 1.5¹) and keeping only the latest version of anything changed through incremental updates. It does not recompress images and does not remove every unused item, so a file that is mostly photos, or one already saved compactly, may barely change. Recommended and Maximum replace every page with a lower-resolution picture, which removes most of the image data in scans and photo-heavy files, but adds data to text-only pages: a picture of a page holds far more than the characters on it.

Our test: the same files at every level

We used three sample files:

• Photo-heavy PDF (3.3 MB): three A4 pages showing the same large photo (3840 × 2400 pixels, stored once in the file), twelve lines of text on each page, and on page 1 a web link and a filled-in form field.
• Text PDF (11.6 KB): four A4 pages of text with a link and a filled-in form field, saved without object streams.
• Compact text PDF (13.7 KB): ten pages of text with a link and a form field, already saved with object streams.

We then opened each compressed file and checked what was left:

• Both Basic results still had all of their selectable text, the working link and the form field with its value.
• The Recommended and Maximum versions of the photo-heavy PDF had no selectable text, no clickable link and no form field. The link text and the typed value were still visible as part of the picture.

Limitations

• One PDF at a time, up to 200 MB. Very large files are processed in your browser’s memory and can be slow on older phones and computers.
• Password-protected PDFs must be unlocked in a PDF reader first.
• There is no target-size setting: you choose a level and see what it achieves.
• Recommended and Maximum remove selectable text, links, form fields, bookmarks and document properties, as described above.
• Any level rewrites the file, so a digital signature will no longer validate.

Troubleshooting

“This PDF could not be made smaller at this level”

The file contains little that this level can remove. For a text PDF, Recommended and Maximum would make it bigger; try Basic, or keep the original. If Basic cannot help either, the file is probably already compact.

The file is still over an upload limit

• If you can accept losing selectable text, links and forms, try Recommended, then Maximum, and check the size shown.
• Send only the pages that are needed: Split PDF extracts selected pages into a new file without changing their quality.
• If you are building the PDF from photos with JPG to PDF, which keeps images at their original quality, make the photos smaller first with the Image Resizer.
• Share a link instead of attaching the file. Personal Gmail accounts, for example, allow 25 MB attachments and turn larger ones into Google Drive links⁴.

The text looks blurry after compression

Maximum uses a lower resolution and stronger JPEG compression than Recommended. Click Try a different level and use Recommended, or keep the original for documents with small print.

The tool says the PDF is password-protected or damaged

Open it in a PDF reader, remove the password or save a new copy, then try again. A file that will not open in a reader cannot be compressed either.

Common questions

Does compressing a PDF reduce image quality?

Basic does not change images. Recommended and Maximum redraw every page as a JPEG at 150 or 100 DPI, so photos and text lose some detail; Maximum loses more.

Will my compressed PDF still be searchable?

With Basic, yes, if the original was searchable. With Recommended or Maximum, no: the text becomes part of an image. A scanned PDF was never searchable to begin with unless OCR was applied².

Why did my text-only PDF not get smaller?

Text PDFs are usually compact already, and turning their pages into images adds data rather than removing it. ToolSolvo compares the sizes and tells you when there is no saving instead of giving you a larger file.

Can I compress a PDF to an exact size, such as under 1 MB?

Not with a guarantee, and ToolSolvo has no target-size setting. Try the levels in turn and check the size shown; if it is still too large, use the steps under Troubleshooting.

Is my file uploaded?

No. The PDF is processed in your browser on your own device and is not sent to a server. As with any tool, keep your original until you have checked the compressed copy.