PDF too large to email? Compress it in seconds.

Gmail has a 25 MB total attachment limit per email. This covers all attachments combined, not each one individually. If your PDF is over 25 MB, Gmail will prompt you to send it via a Google Drive link instead. If the recipient uses a different email provider with a lower limit, they may still not receive it even if Gmail lets you send it.

Microsoft personal Outlook.com accounts allow up to 25 MB. However, corporate Exchange servers are configured by IT departments with their own limits — often 10 MB or even less. The limit your recipient's company sets is what matters for delivery. If you're getting bounce-back messages from corporate recipients, compress to under 10 MB to be safe.

It depends heavily on what's in the PDF. Scanned document PDFs — which are essentially images — can often be compressed by 70-90% because high scanner DPI creates unnecessarily large image data. Text-based PDFs (created digitally, not scanned) compress much less, usually 10-30%, because text is already efficient. A 50 MB scanned contract might compress to 5 MB with good quality. A 2 MB text report might only reach 1.5 MB.

For non-sensitive documents, online compressors are convenient. For anything confidential — contracts, financial statements, legal filings, HR documents, medical records — using an online tool means uploading that content to a third-party server. You have no control over how long they keep it, who can access it, or their security practices. Desktop tools like Diwadi compress everything locally, so your documents never leave your computer.

The most common cause is scanned documents with high DPI settings. A scanner set to 600 DPI produces images roughly 9x larger than 200 DPI, with minimal visual improvement on screen or in print. Other causes include embedded high-resolution images inserted into Word before converting to PDF, uncompressed fonts embedded throughout the document, and duplicate image data where the same image appears multiple times without optimization.

Compress if the recipient needs the complete document and content quality allows it. Split if the PDF is a collection of separate documents, the content is at minimum quality already, or different sections need to go to different people. For most business documents — a 40-page contract or a 30-page report — compression to hit an email limit is the right approach. Splitting is better for large portfolios or multi-section deliverables.

Compressing a digitally signed PDF can invalidate the signature, because compression changes the file's binary data, which breaks the cryptographic hash the signature verifies. If your PDF has an existing digital signature that needs to remain valid, do not compress it. Instead, split out only the pages you need to send, or use a file sharing service. If the signature doesn't need to remain valid, compression works normally.

PDFs contain two types of content: vector text/graphics (resolution-independent, tiny file size) and raster images (pixel-based, large file size). PDF compression primarily targets raster images using JPEG compression. 'Reducing quality' refers to the JPEG compression level applied to those embedded images. High quality = larger file with sharper images. Low quality = smaller file with more visible compression artifacts. Text and vector elements are not affected by quality settings.

If compression can't get your PDF under the limit without destroying quality, your options are: (1) Use Google Drive, Dropbox, or OneDrive to share via link — paste the link in the email instead of attaching. (2) Use a file transfer service like WeTransfer. (3) Split the PDF into smaller sections and send in multiple emails. (4) Print to PDF with lower image quality settings if the original was created in Word or another application.

Yes. Diwadi is a desktop application that runs entirely on your computer. PDF compression happens locally using your computer's processor — no internet connection required at any point. This is particularly important for sensitive documents that shouldn't be transmitted over the internet at all. You can compress PDFs on a plane, at a client site with no Wi-Fi, or on an air-gapped computer.