Email attachment limits are a familiar problem. Your PDF is a perfectly good document until the moment you try to send it, at which point it is suddenly 2MB too large for the recipient's mail server. Here is how to reduce the file size quickly enough that it stops being a problem.
What the limits actually are
Email attachment limits vary by provider and company mail policy:
- Gmail, 25MB total per email (all attachments combined)
- Outlook.com / Hotmail, 20MB per email
- Microsoft 365 (business), 25MB to 150MB depending on IT settings; your company's mail server may have its own, lower limit
- Apple Mail via iCloud, 20MB, with Mail Drop for larger files
- Company mail servers, often 10MB to 25MB, set by the IT department and not displayed anywhere obvious
In practice, the effective limit for safe email sending to an unknown recipient is around 10MB. Mail servers along the delivery chain (not just the sender and recipient) may apply their own limits, and a 24MB attachment that clears your server may bounce at the recipient's.
For guaranteed delivery without thinking about it, compress to 10MB or below for most business emails.
The fastest approach: target-based compression
Open PDFWhisk's compressor, drop in your PDF, and choose a target size that puts you safely under the relevant limit. For email, 10MB is a sensible default unless you know the recipient's exact limit. If you are sending to a Gmail address and the attachment is the only file in the email, 20MB is safe.
The compression runs in your browser, no upload, no waiting for a server. For typical PDF sizes up to 50MB, the process takes a few seconds. Download the compressed file, attach it to your email, and send.
If the PDF is still too large after compression
Some files resist compression because they are already efficiently encoded, or because removing enough data to reach the target would make the document unreadable. In these cases:
Remove pages you don't need first. If you are sending a 30-page report and the recipient only needs pages 5-12, use PDFWhisk's delete pages tool to trim it to 8 pages before compressing. Less content means a smaller file and better compression quality.
Use a cloud sharing link instead. For very large files, portfolios, brochures, lengthy contracts, Google Drive, Dropbox, or OneDrive links are simpler than working around size limits. Upload the file, generate a shareable link, and paste it into the email. The recipient clicks the link rather than downloading an attachment. This is also better for version control if you might update the document.
Split the document. If the recipient genuinely needs everything and the file cannot be compressed enough, split it into two or three logical sections and send each as a separate email or separate attachment in one email. Most email providers count attachments individually, so two 8MB attachments in one email typically works even when a single 16MB attachment would not.
Sending from a phone
On iPhone: compress the PDF in Safari using PDFWhisk, save it to Files, then share it from Files to your email app. On Android: compress in Chrome, find it in Downloads, and share via Gmail or your email app directly from the file manager.
The compressed file is saved to your phone's storage and can be attached to an email just like any other file. If you are using the Gmail or Outlook mobile app, tap the attachment icon, navigate to the Files or Downloads folder, and select the compressed PDF.
Checking before you send
After compressing, check three things: the file size (should be under your target), the readability of key content (zoom in on small text, figures, and signatures), and the filename (make it descriptive and professional before attaching). These thirty seconds prevent the most common causes of failed or rejected submissions.