How to Compress PDF Files for Email

February 16, 2026

You have a PDF that needs to go out by email, but when you try to attach it, your email client refuses. The file is too large. This is one of the most common frustrations when working with PDFs, and it happens more often than you might expect. Fortunately, compressing a PDF to fit within email limits is straightforward when you have the right tool.

Why PDFs Are Often Too Large

PDFs can become surprisingly large for several reasons. Scanned documents are a common culprit: when you scan a paper document, each page is essentially a high-resolution image, and those images add up quickly. A 10-page scanned contract can easily exceed 20 MB.

Embedded images are another factor. If a PDF contains photographs, charts, or detailed graphics, these elements can inflate the file size dramatically. Even documents created digitally may include embedded fonts, metadata, and structural elements that contribute to their size.

PDFs generated from presentations or design software tend to be especially large because they preserve high-resolution graphics intended for print quality, which is far more detail than what is needed for on-screen viewing.

Common Email Attachment Limits

Different email providers impose different limits on attachment sizes:

• Gmail: 25 MB per email (including all attachments combined)
• Outlook.com: 20 MB per attachment
• Yahoo Mail: 25 MB per email
• Apple iCloud Mail: 20 MB per attachment
• Corporate email: Often 10-15 MB, depending on the organization’s IT policies

If your PDF exceeds these limits, you need to either compress it or find an alternative way to share it. Compression is usually the simplest solution.

How PDF Compression Works

PDF compression reduces file size by optimizing the elements inside the document. The main techniques include downsampling images to a lower resolution, applying more efficient image compression algorithms, removing duplicate resources, and stripping unnecessary metadata.

The key is finding the right balance between file size reduction and visual quality. Aggressive compression produces smaller files but may result in noticeably lower image quality. Light compression preserves quality but achieves a more modest size reduction.

Compressing PDFs with ArmorPDF

ArmorPDF’s Compress PDF tool makes this process simple and private. Here is how to use it:

1. Open the Compress PDF tool in your browser.
2. Drag and drop your PDF file into the drop zone, or click to browse.
3. Choose your compression level: Light (best quality), Medium (balanced), or Strong (smallest file).
4. Click “Compress PDF” and wait a few seconds.
5. Download your compressed file.

The entire process happens in your browser. Your file is never uploaded to any server, which means your documents stay completely private. This is especially important for sensitive materials like financial documents, legal agreements, or personal records.

Tips for Getting the Best Results

Start with the Medium compression level, which offers a good balance for most documents. If the resulting file is still too large, try Strong compression. If you need the document to look its best (for example, a portfolio or a presentation), use Light compression and verify the output quality.

If compression alone does not bring the file under your email limit, consider these alternatives:

• Use the Split PDF tool to break the document into smaller parts and send them as separate attachments.
• Use the Remove Pages tool to strip out unnecessary pages before compressing.
• If the recipient only needs certain pages, extract just those pages using the Split tool.

Compress Without Compromising Privacy

Unlike most online compression tools that require uploading your files, ArmorPDF processes everything locally. No signup, no waiting for server processing, and no risk of your documents being stored on someone else’s computer.