How to Compress a PDF and Reduce Its Size

▶ 1. Why a PDF gets too heavy

In most cases the weight does not come from the text but from the images: very high resolution scans, photos inserted at full quality or pages produced by a scanner generate files of dozens of megabytes, often beyond the limits for email attachments.

Compressing means resampling those images to a resolution suited to how the document will really be used. A file meant for reading on screen does not need the same density as one destined for professional printing: that difference is exactly what the compression profiles work on.

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Unlike online compressors, the PDF here is not sent to a server to be processed: the whole operation happens on your computer, inside the browser tab.

⇲ 2. Compressing the PDF step by step

A few clicks are enough: open the document, choose a profile and download the lighter version. No desktop software to install — 123 PDF Editor PRO is a Chrome extension and works on Windows, Mac and Linux.

Compressing a PDF locally with the Web, Email or Print profiles — Reduce the size with the Web, Email or Print profiles — entirely on your device.

Install the extension from the download page and open it by clicking its icon in the toolbar.
Click Choose a PDF (or Open PDF) and select the file to make lighter.
Open the Compress tool and choose a profile: Web, Email or Print.
For finer control, adjust the resolution (DPI) and the image quality by hand; you can also convert the pages to greyscale.
Switch on Preserve selectable text, links and form fields to keep selectable text, links and interactive form fields.
Click Compress and download and save the new file to your computer.

▤ 3. Which profile to choose

The three profiles are ready-calibrated shortcuts: they start from sensible settings for the intended use of the document, so you do not have to think in DPI.

Profile	When to use it	Result
Web	Documents to publish online or read on screen	Maximum reduction
Email	Attachments to send, with size limits to respect	Good compromise
Print	Files destined for printing, where detail matters	Conservative reduction

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When in doubt start with Email: if the file is still too heavy move to Web, while if image quality suffers too much step up to Print.

◎ 4. Reducing without ruining the document

Compression is a trade-off between weight and quality: a few precautions help you avoid losing what really matters.

✓ Keep the text selectable. With Preserve selectable text, links and form fields switched on, the document stays searchable and forms keep working.
✓ Do not push the DPI too low if the PDF is going to be printed: on screen the drop is barely noticeable, on paper it shows.
✓ Greyscale only makes sense for documents that do not need colour, such as text scans — but the saving is considerable.
✓ Check the result before sending it: open the downloaded file and look at the pages with the most delicate images.

▦ 5. Other ways to make a PDF lighter

If the file is still bulky after compression, the problem is usually the content: too many pages or needlessly large images.

Organising PDF pages with draggable thumbnails — Remove or extract the pages you do not need before compressing: it is the most effective reduction of all.

Open Organize pages and delete the pages you do not need, or use Extract selected pages to export only the part that interests you.
With Split PDF you can break a very long document into several lighter files to send separately.
Replace oversized images with lighter versions using Replace with local image.
In Privacy cleanup you can remove embedded attachments and other hidden data that take up space.

? 6. Frequently asked questions

The questions that come up most often on this topic.

How much smaller does the file get?

It depends on the content: a PDF made of high-resolution scans can shrink dramatically, while a text-only document is already compact and gains little. The best way to find out is to try the profiles in order.

Does compression ruin the text?

No: compression works on the images. By keeping the option that preserves text, links and form fields switched on, the words stay crisp and selectable.

Can I compress a confidential PDF?

Yes, and this is exactly where the approach pays off: the file is not uploaded to any server, so it never leaves your computer. It also works without an internet connection.

How many times can I compress for free?

The free version includes every tool with a limit of 5 PDF downloads and 3 saved projects in total. The PRO licence is a one-time payment of $24 that removes the limits, with no subscription.

How to compress a PDF and reduce its size