TL;DR: Open PDFKits Compress PDF, drop your file, pick a target size, download. Free, in your browser, no upload to any server. The rest of this page explains email provider limits and target-size strategy.
Email providers cap the total message size (PDF + email body + other attachments). Current limits: Gmail 25 MB. Outlook.com / Microsoft 365 20 MB by default (admins can lower to 10 MB). iCloud Mail 20 MB. Yahoo Mail 25 MB. Corporate Exchange typically 10 MB (often lower for inbound). ProtonMail 25 MB free, 100 MB paid. If your PDF is over these limits, compress before sending — otherwise the email bounces.
1. Open the tool. Go to Compress PDF in your browser. No signup required, no software to install. 2. Drop your file. Drag your PDF into the upload zone or click to browse. The file stays in your browser memory — nothing is uploaded to a server. 3. Pick a target size. For Gmail/Yahoo, aim for <25 MB. For Outlook/Exchange, target <10 MB to be safe across all corporate setups. 4. Download. Click Compress and the result downloads instantly. Email it.
Direct shortcuts to dedicated PDFKits compressors with preset targets:
Email-related PDFs often contain sensitive content: contracts, invoices, IDs, medical records. Uploading them to a remote compression service is a privacy risk. PDFKits compresses entirely in your browser using JavaScript and WebAssembly — your PDF never leaves your device. The compressed result goes straight to your downloads folder, then to your email. For related guides: Compress PDF for Resume, PDF Compression Benchmark.