---
title: How to compress a PDF on a Mac without ruining the text
source: https://arazioformac.com/notes/compress-pdf-on-mac-without-ruining-text
---

# How to compress a PDF on a Mac without ruining the text

A 40 MB PDF will not attach to an email. You compress it, it comes back at
8 MB, and later you discover you can no longer select a single word in it,
search it, or copy a phone number out of it. Every page has become a
photograph of itself.

That is not a bug in the tool you used. It is how most PDF compressors work,
and it cannot be undone.

**The one-gesture way**

1. Pick the file up in Finder, as if you were moving it.
2. Hold `⌥`. A ring of tools appears around the cursor.
3. Let go toward **Compress**. The new file lands beside the original.

Six tools work on PDF files — hold ⌥ and they appear around the cursor:
Compress, Extract Pages, Merge, Rotate, Split, Strip Metadata.

Six actions work on any file at all — hold ⌃, including on files Arazio cannot
convert: AirDrop, Shelf, Copy, Move, Copy Path, Terminal.

That is the whole thing. It works on one file or four hundred, and
nothing is uploaded — the compression happens on your Mac.

[Arazio](https://arazioformac.com) subsets the embedded fonts instead of
rasterising the pages, so the words stay words. It then renders the result and
compares it against the original pixel by pixel, and throws its own work away
if anything moved — so compressing can never change how a page looks. $9.99
once.

The rest of this page is why PDFs get large, and what the free routes do.

## First: what is big inside it?

PDFs get large for two completely different reasons, and the fix is different
for each.

**A scan or a photo album.** Every page is a picture. The bytes are image data
and the only way to shrink it is to re-encode those images at lower quality.
You will lose some visual detail. There is no text to lose, so nothing else is
at risk.

**A document out of Word, Excel, PowerPoint or Pages.** The pages are text.
Often there is not a single photograph in the file — and it is still 30 MB.
The weight is in the **embedded fonts**.

That second case surprises people, so here is a real example. A 31-page
report, produced by Word, 597 KB. No images at all. It embedded ten typefaces
carrying **4,551 glyphs**, for a document that uses **85 distinct
characters** — and it embedded Arial twice, byte for byte identical.

Nearly the whole file was alphabets nobody was going to read.

## What "Reduce File Size" does, and why it often fails

macOS has a built-in option: open the PDF in **Preview**, then **File → Export
→ Quartz Filter → Reduce File Size.**

Free, already there, and worth trying first. Two things to know:

- On a scan it works, and can be aggressive — it downsamples images to 72 dpi,
  which is fine on screen and poor in print.
- **On a text document it frequently makes the file bigger.** It has nothing to
  take from a page of words, and the re-encode adds overhead.

If Preview hands you back something larger, that is not you doing it wrong.
That is the tool meeting a file it has no answer for.

## Why online compressors can ruin the text

Many of them rasterise. Each page is rendered to an image, the images are
JPEG-compressed, and a new PDF is built from the pictures. The file gets
dramatically smaller, which is why the number looks so good.

What you lose:

- Selecting, copying and searching text
- Screen readers, so the document stops being accessible
- Crisp text when zoomed — letters go soft and blocky
- Any chance of getting it back

And the file was uploaded to someone else's server to have it done.

A compressed PDF that you can no longer search is often worse than the large
one you started with. If it is a contract, an invoice or anything you may need
to find a number in later, this matters more than the megabytes.

## How to tell if it happened to you

Open the compressed PDF and try to select a line of text with the cursor.

If you can highlight individual words, the text survived. If the whole page
highlights as one block, or nothing highlights at all, your document has
become a stack of pictures.

Do that check **before** you delete the original.

## The right fix for a text PDF: subset the fonts

A PDF does not need the whole alphabet of every typeface it uses. It needs the
characters on its pages. Cutting an embedded font down to those is called
subsetting, and it is lossless — the words stay words, the layout does not
move, and nothing is rendered to a picture.

On that 31-page report, subsetting the fonts took **27% off the file with
every page rendering identically.**

The catch is that macOS gives you no way to do it. Preview cannot, and neither
can most compressors, because they are built around the scan case.

## The honest limit

Some PDFs cannot be made smaller by anything, and you should be suspicious of
a tool that claims otherwise.

If a document is already tightly packed — a well-made PDF with subset fonts
and compressed images — there is nothing left to take. Arazio says so, in
those words, and gives you back the file you started with rather than a copy
that is somehow larger.