How to Reduce PDF File Size for Email Attachments

There's nothing quite like the frustration of trying to email an important document, only to get rejected because the file is too large. Gmail's limit is 25MB. Outlook is 20MB. Many corporate email servers are even more restrictive. And somehow, your PDF is 32MB.

I've been there more times than I can count. Over the years, I've learned exactly how to slim down PDFs without destroying their quality. Let me walk you through what actually works.

Why Are PDFs So Big Anyway?

Understanding why a PDF is large helps you know how to fix it. The usual suspects:

• High-resolution images. A single 300 DPI photo can be 5-10MB. A document with several such images balloons quickly.
• Embedded fonts. Including full font files ensures consistent display but adds megabytes.
• Scanned documents. Scans at high DPI create massive files, especially color scans.
• Unnecessary elements. Hidden layers, bookmarks, embedded files, and metadata all contribute.
• Linearized for web. Sometimes called "fast web view," this adds redundant data for streaming but increases overall size.

Quick Methods That Actually Work

Method 1: Use Online Compression

The fastest approach. Our PDF compression tool reduces file size while maintaining readability. You drag in your file, it processes locally in your browser, and you download a smaller version.

For most documents, you can get 40-70% size reduction with minimal visible quality loss. Text stays sharp. Images might lose a tiny bit of crispness, but they're usually still perfectly acceptable for professional use.

Method 2: Reduce Image Resolution

If your PDF contains images, this is where the real savings are. Most documents don't need images at 300 DPI — 150 DPI is usually fine for on-screen viewing and even most printing.

In Adobe Acrobat: File → Save as Other → Reduced Size PDF

This gives you options for image downsampling. Choose 150 DPI for screen-optimized PDFs, 300 DPI for print-optimized.

Method 3: Convert Scanned Color to Grayscale

If you're dealing with scanned documents, color adds massive file size. Unless color is genuinely important (photos, diagrams with color-coded information), convert to grayscale.

A color scan might be 15MB. The same document in grayscale? Maybe 3MB.

Method 4: Remove Unwanted Elements

PDFs sometimes contain hidden data that you don't need:

• Embedded fonts (if standard fonts are acceptable)
• Hidden layers and objects
• Bookmarks and links you don't need
• Document metadata
• Embedded files and attachments

Tools like our PDF optimizer can strip these automatically.

Method 5: Re-save as PDF

Sometimes just opening a PDF in a different application and re-saving it results in a smaller file. Different PDF writers have different compression algorithms.

Try opening your PDF in Preview (Mac) or Chrome and printing to PDF. The new file might be significantly smaller.

Compression Quality Settings Explained

When you compress a PDF, you're usually trading quality for size. Understanding the settings helps you make the right choice:

High Quality / Low Compression

Best for: Professional documents, presentations, anything that will be printed

Result: 10-30% size reduction, nearly indistinguishable from original

Medium Quality

Best for: Business documents shared internally, reports, forms

Result: 40-60% size reduction, slight image softening, text remains clear

Low Quality / High Compression

Best for: Quick previews, documents where appearance matters less

Result: 70-90% size reduction, noticeable image artifacts, acceptable text

When Not to Compress

Compression isn't always the right answer. Skip aggressive compression when:

• The document contains fine detail (architectural drawings, technical diagrams)
• It will be professionally printed (printers need high-resolution files)
• It contains text that will be OCR'd (compression can interfere with text recognition)
• It's a legal document where integrity matters (some compression alters document structure)

Alternatives to Compression

If compression isn't getting you under the size limit, consider alternatives:

Cloud Storage Links

Upload to Google Drive, Dropbox, or OneDrive and share a link instead of attaching the file. This bypasses email attachment limits entirely.

Split the Document

If you have a 50-page PDF, split it into smaller parts. Our PDF split tool lets you break documents at specific pages. Send the most important pages, or send multiple emails with smaller attachments.

Use a File Transfer Service

Services like WeTransfer let you send files up to 2GB for free. You upload, enter the recipient's email, and they get a download link.

A Real Workflow Example

Let's say you have a 28MB PDF report to email via Gmail (25MB limit):

1. First, try our compression tool. Set to medium quality. This typically gets you a 10-15MB file.
2. If that's not enough, check if the document has high-res images. Convert images to 150 DPI.
3. Still too large? Consider if all pages are necessary. Split out the essential pages.
4. As a last resort, use a cloud storage link instead of attachment.

The Bottom Line

PDF compression for email is usually straightforward. Use a compression tool first — it solves most size problems in seconds. If you need more control, look at image resolution, color depth, and unnecessary elements.

Keep in mind that aggressive compression degrades quality. For important documents, test that the compressed version is still acceptable before sending. Nothing worse than realizing your client received a blurry, unreadable document.