How to Reduce PDF File Size for Email

Text takes almost no space in a PDF. A hundred pages of plain text is a few hundred kilobytes. When a PDF is 30 MB, the weight is nearly always photographs, scans or embedded graphics. Every fix below is a way of dealing with those images.

First, know the limit

Email services cap the size of a message including its attachments. Gmail's limit is 25 MB, and many others are similar or lower. Company mail servers are often stricter. Attachments are also encoded for transport, which adds roughly a third to their size, so a file close to the limit may still be rejected. Aim for well under 10 MB when you can.

Method 1: Export again with a smaller-size option

If you created the PDF from a document, go back to the source and export again:

• Microsoft Word: choose Save As, pick PDF, and select Minimum size (publishing online).
• Google Docs, Pages and others: reduce the size of large images in the document before downloading as PDF.
• Design tools: look for a “web” or “screen” PDF preset rather than “print”.

This is the cleanest fix because the images are scaled down from the originals rather than being compressed twice.

Method 2: Compress the images before making the PDF

For PDFs built from photos, such as pictures of receipts or documents, shrink the photos first:

1. Run them through the Image Compressor with a maximum width of about 1600 pixels and quality around 70. Text in a photographed page remains readable at that size.
2. Combine the smaller images with JPG to PDF.

Ten phone photos at 4 MB each make a 40 MB PDF. The same ten compressed this way typically come to a few megabytes.

Method 3: Use the built-in option on a Mac

Open the PDF in Preview, choose File → Export, and pick Reduce File Size from the Quartz Filter menu. It is quick, but the default filter is aggressive and can make images look rough. Check the result, and keep the original.

Method 4: Rescan with sensible settings

If the PDF came from a scanner or scanning app, the settings matter far more than any later compression. For ordinary paperwork use greyscale or black and white rather than colour, and 150 to 200 dpi rather than 600. Many scanning apps have a “document” mode that does this for you.

Method 5: Split it, or send a link instead

Sometimes a document legitimately needs high-quality images. In that case:

• Send it in parts, each under the limit, with clear names such as “Report part 1 of 3”.
• Upload it to a cloud storage service such as Google Drive, OneDrive or Dropbox and email a sharing link. Check the link's permissions so the recipient can actually open it.

What not to worry about

Removing a few pages of text, changing fonts or zipping the file will not make a meaningful difference. Find the images, and you have found the megabytes.