Find out why the PDF is big
- It came from a scanner or a phone camera. Each page is a large picture of paper. Scans at 300 dpi or more, or in colour when black and white would do, are the usual cause. Compressing at 150 dpi removes most of the size: our colour test scan went from 1.2 MB to 234 KB.
- It was exported from a presentation or a design program. Pictures there are often much larger than they are shown, and some programs store them without compression. This is where the biggest savings are: in our test, five slides that shared an oversized photo and logo went from 38 MB to 80 KB.
- It has high resolution photos. A report with a dozen photos from a camera can be 30 MB. Photos at 150 dpi at the size they appear look the same on screen.
- It is long, but only text. A PDF of several hundred pages of text may be a few megabytes. There are no pictures to shrink, and compressing saves little.
Other ways to reduce the size
- Remove pages you do not need. Split PDF can take out the pages that carry the heavy pictures, or send only the pages someone asked for.
- Scan smarter. Scan at 150 to 200 dpi, in grey or black and white if colour does not matter, before you ever make the PDF.
- Rebuild from the pictures. If you have the original photos, the Image to PDF tool can make a new PDF at a size you choose.
- Export differently. Most word processors and presentation programs have an export option called minimum size or web quality.
Size on disk and size in an email
Email adds about a third to the size of an attachment, because attachments are encoded as text. A 10 MB PDF can fail to send where the limit is 10 MB for the whole message. Aim for a PDF well under the limit, and compress again with Smallest if you are close.