You've created or received a PDF and it's far larger than it should be. Maybe your email client won't send it, a web form won't accept it, or it just takes too long to download. Here's a systematic guide to diagnosing and fixing oversized PDFs.
Diagnosing your specific situation
Not all large PDFs have the same cause, and the right solution depends on which category yours falls into. Spend 30 seconds on diagnosis before trying to compress.
Open the PDF and look at the content. Lots of photographs on every page? The images are almost certainly the cause — compression will help significantly. Plain typed text on white backgrounds with no images? The PDF shouldn't be large at all — something else is going on, likely metadata, embedded fonts, or revision history. Scanned pages? The entire document is images, even if it looks like typed text — standard compression applies but the results depend on the original scan quality and DPI.
Solution 1: Use targeted compression for specific size limits
If you need to hit a specific file size limit — a portal that accepts PDFs up to 200KB, an email system that caps attachments at 500KB — PDF99 has dedicated tools that automatically find the right quality setting to reach the target.
- Compress to 50KB — for government portals and strict form upload limits
- Compress to 100KB — for job application and HR portals
- Compress to 200KB — the most common document submission limit
- Compress to 500KB — for email and general sharing
Each tool tries progressively lower quality settings until the output fits within the target size. You don't need to experiment manually.
Solution 2: Split the document if only part is needed
If you're trying to email or upload a large document but the recipient only needs part of it, extracting the relevant pages is often the best solution. A 50-page report where the recipient needs chapter 3 (pages 18-27) is much easier to handle as a 10-page extract than as a compressed version of the full report. The extract will be smaller, load faster, and be more directly useful.
PDF99's split tool lets you select specific pages using visual thumbnails or a page range like 18-27. Download the selection as a clean single PDF or as individual page files in a ZIP.
Solution 3: Re-create digitally if the PDF is a scan of a typed document
This sounds like more work than it is and is often the best solution. If your large PDF is a scanned photograph of a typed document — a contract, a letter, a certificate — and you have access to the original typed version, exporting it directly to PDF from the source application produces a dramatically smaller file. A Word document exported to PDF is typically 100-500KB. A scan of the same printed document is typically 2-10MB. The digital export is also higher quality, searchable, and doesn't have the slightly soft appearance of scanned text.
Solution 4: Check if the file is encrypted or password protected
Password-protected and encrypted PDFs sometimes don't compress well because their content streams are already encrypted, making further compression less effective. If your large PDF is protected, removing the protection first (if you have the password and authorisation to do so) may allow the compression tool to work more effectively on the underlying content.
When nothing works
If you've tried compression and the file still exceeds your size limit, consider these alternatives. Upload to Google Drive or Dropbox and share a link rather than an attachment — most portals and email systems that cap file sizes are fine with a Drive link to a larger file. For portal uploads specifically, contact the portal administrator — many size limits are set conservatively and can be raised for legitimate professional documents. For email specifically, consider whether the recipient actually needs the full document or whether a summary with a link to the full version would serve the purpose better.
Size limits by context: a quick reference
Knowing the typical size limit for your context helps you choose how aggressively to compress. Here are the most common limits you'll encounter.
Email (Gmail, Outlook): 25MB per email total. In practice, keep PDF attachments under 10MB so there's room for other attachments. Very large PDFs are better shared via Google Drive link.
WhatsApp: 100MB per file for documents. But files over 16MB can be slow to send and open on mobile connections. Aim for under 5MB for any document you expect recipients to open on their phones.
Job application portals: Most commonly 2MB, 5MB, or 10MB per document. Some older portals cap at 200KB or 500KB for supporting documents. Check before uploading — portal error messages about file size sometimes don't appear until after you've already tried to submit.
Government and council portals: Often the most restrictive — 50KB to 500KB is common. If a government portal is rejecting your PDF, the target-size compression tools are the fastest solution.
University submission portals (Turnitin, Canvas, Moodle): Typically 20MB or higher. Rarely a practical issue unless you're submitting a large design portfolio or multimedia coursework.
Cloud storage (Google Drive, Dropbox, OneDrive): No meaningful per-file limit for PDFs in practice. Storage quota limits apply to total account usage, not individual files.
When the portal claims your file is fine but still rejects it
Sometimes a portal reports that your file is under the size limit but still rejects it. This usually means a secondary restriction is in play. Common secondary checks portals run include: total page count (some portals cap at 10 or 20 pages regardless of file size), PDF version (very old portals may not support PDF 1.6 or later features), password protection (portals almost always reject encrypted PDFs), and file corruption (a PDF that looks fine in your viewer may have structural issues that portal validation catches).
For the page count issue: use PDF99's split tool to extract the specific pages you need rather than sending the full document. For password protection: remove it before uploading (the tool for this is coming soon on PDF99 — for now, printing to PDF removes most protection). For corruption: open the PDF in a browser tab, use the browser's print function, and save as PDF. This re-generates a clean file from the rendered content.