Getting the most out of PDFs

Compress a PDF or cut its page count: which do I need?

If the file will not attach to an email you need compression; if the document is tedious to read or expensive to print you need fewer pages. Compression never removes a page and combining pages barely changes the file size.

3 min read

Compress PDFShrink heavy files, keep the text sharpSmartShrinkCut the page count, not the text sizeSplit PDFExtract a range or split into separate files

"Make this PDF smaller" can mean two different things, and picking the wrong one wastes an afternoon.

The ten-second test

Ask what went wrong.

  • "It will not attach." That's megabytes. You need Compress PDF.
  • "It is ninety pages and I have to print it." That's sheets. You need SmartShrink.
  • "It takes forever to scroll through." Sheets.
  • "It is slow to open." Usually megabytes, sometimes a very large number of images.

Neither tool helps with the other's problem. Compression will not remove a page. Combining pages will barely change the file size, because the text was never what made it heavy.

What compression does

A PDF's weight is almost always its images. Compression saves them again at a lower resolution or stronger JPEG compression, keeps only the characters of each font that the document uses, and removes parts of the file that are repeated or unused.

What this means in practice:

  • A scanned document compresses enormously, because it is entirely images. Ten megabytes to one is ordinary.
  • A text document barely compresses, because there is nothing heavy in it. If a 3 MB text-only PDF only reaches 2.6 MB, nothing went wrong. There was nothing else to remove.
  • Compression is lossy for images. Push it hard and photographs go soft and scanned text gets mushy. The levels exist so you can choose where to stop.

What reducing page count does

It changes the layout. Pages that are mostly empty are stacked onto single sheets at their original size, so the text stays the same and the document gets shorter.

The file size afterwards is roughly what it was. Occasionally a little smaller, because there are fewer page objects; never dramatically. If the number of megabytes is what you are watching, this is the wrong tool.

When you need both

A long scanned report is heavy *and* long. Do it in this order:

  1. Reduce the page count first. Fewer pages means fewer images to process afterwards.
  2. Compress second, so the compression runs on the final document.

Doing it the other way round works too, but you compress pages you are about to throw away.

The limits

  • Compressing an already-compressed PDF gains almost nothing. Saving the images again at a lower quality makes them worse without saving much space.
  • Reducing page count on a dense document gains almost nothing either. If a dense document suddenly has far fewer pages, the text was shrunk to get there.

Know both before you start. Each one looks like the tool failing, but it isn't.

Common questions

Why did compression barely change my file?

Because it was mostly text. Compression works on images, fonts and redundant objects; a text-only PDF has very little of any of those to remove.

Does reducing the page count make the file smaller?

Only slightly. The same content is still there, arranged onto fewer sheets. You save a little from having fewer pages, but the content itself is the same size.

Which should I do first?

Page count first, then compression, so the compression runs on the finished document rather than on pages you are about to combine.

Related guides

Getting the most out of PDFsWhy won't my PDF attach to an email?Almost always because the file is over the recipient's size limit, which is often lower than your own, and attachments grow by roughly a third in transit, so a 24 MB file is really 32 MB.Getting the most out of PDFsWhy is my PDF so large, and what actually makes it smaller?Almost always images: a scan or a photo-heavy document is mostly picture data, and re-encoding those images is what reduces the size; text and vectors take almost no space at all.Getting the most out of PDFsHow do I print a long PDF on fewer sheets of paper?Double-sided printing halves the sheets for nothing; your printer's own 2-up halves them again at about 70% size; and rebuilding the PDF so sparse pages share a sheet reduces the count with the text left at full size.