PDF Tools

Compress PDF on iPhone

Reduce PDF file size on iPhone for email attachments, uploads, and faster sharing. Choose a quality level and preview the savings before exporting.

Smaller files Email ready Preview savings On-device only

Best for: attachments, portals, and cloud uploads where the document is already correct but too large to send comfortably.

What does PDF compression do, and how much smaller can a PDF get?

PDF compression reduces the file size of a PDF by re-encoding its embedded images at a lower quality or resolution, while keeping text, vector graphics, and document structure fully intact. On iPhone, PDF compression typically shrinks a scanned document by 35–70% depending on the chosen quality level: Maximum reduces size by about 15%, High by 35%, Medium by 55%, and Low by up to 70%. ScanLens runs compression on-device, so the original file never leaves your iPhone during processing.

Compression solves a size problem, not a page-selection problem. If the PDF is already correct but too heavy to email, upload, or store efficiently, this is the right tool.

If you need to combine files first, use Merge PDF. If you only need certain pages, use Split PDF. Compression is for keeping the same document while making the file smaller.

That is why this page targets attachment and upload intent: reducing file size without rebuilding the document from scratch.

Compression also pairs well with the handoff stage of a workflow: prepare a signed file for delivery with PDF signing, add password protection, or send the lighter version through your scan-to-cloud workflow.

How PDF Compression Works

Image Recompression in PDFs

Most PDF file size comes from embedded images. Compression re-encodes these images at lower quality, dramatically reducing size. A 5MB photo becomes a 500KB image—still clear enough to read, but 10x smaller.

Text and Vector Preservation

Text and vector graphics (lines, shapes, charts) aren't affected by compression. These elements remain perfectly sharp regardless of compression level. Only raster images (photos, scans) are recompressed.

Compression Algorithm Selection

ScanLens uses intelligent compression that analyzes each image type. Photos get JPEG compression. Diagrams get optimized PNG treatment. The algorithm chooses the best approach for each embedded element.

Compression Levels

Quality vs file size tradeoff

Compression is a judgment call, not a binary switch. The right level depends on whether the PDF is headed to print, email, web upload, or long-term storage.

Level	Quality	Typical Reduction	Best For
Maximum	90%	~15% smaller	Photos, portfolios, print-quality docs
High	70%	~35% smaller	Email attachments, general sharing
Medium	50%	~55% smaller	Screen viewing, web uploads
Low	30%	~70% smaller	Archival, text documents, drafts

Choosing the Right Compression Level

Maximum Quality: Use when image quality matters—photography portfolios, design documents, or files destined for printing. Minimal size reduction but maximum visual fidelity.

High Quality (Recommended): The sweet spot for most uses. Noticeable size reduction with minimal visible quality loss. Perfect for email attachments and professional sharing.

Medium Quality: Significant compression for screen viewing. Images look fine on displays but may show artifacts if printed large. Good for web uploads and quick shares.

Low Quality: Maximum compression for smallest files. Text remains readable but photos look soft. Use for archival storage, text-heavy documents, or when file size is critical.

When to Compress vs Keep Original PDF

Compress PDF for Email Attachments

Most email services limit attachments to 25MB. Gmail, Outlook, and Yahoo all enforce this. If your PDF exceeds the limit, compress it. High Quality usually brings files under the threshold while maintaining readability.

Compress PDF for Cloud Storage

Free cloud tiers offer limited space—15GB for Google Drive, 5GB for iCloud. Compressing archived documents frees storage for more files. Low Quality works well for documents you rarely access.

Compress PDF for Faster Downloads

Sharing documents via link? Recipients download faster when files are smaller. A 50MB PDF takes minutes on slow connections; a 10MB compressed version downloads in seconds.

Keep Original for Print and Archive

If the PDF will be printed professionally, keep the original high-resolution version. Compression artifacts become visible in print. For legal archives requiring exact reproductions, also keep originals.

Send Limits

Email attachment size limits

Compression usually exists because another system has a hard ceiling. Use these limits to decide whether to compress further, split the file, or switch to link sharing.

Email Provider	Attachment Limit	Workaround
Gmail	25 MB	Auto-converts to Google Drive link
Outlook	20 MB	OneDrive integration
Yahoo Mail	25 MB	Dropbox integration
iCloud Mail	20 MB	Mail Drop for larger files
Corporate Email	10-25 MB (varies)	Check with IT

When a compressed PDF still exceeds limits, consider splitting the document or sharing via cloud storage link instead of attachment.

Frequently Asked Questions

How much can PDF compression reduce file size?

Typical results by compression level: Maximum quality reduces by ~15%, High quality by ~35%, Medium by ~55%, and Low by ~70%. Actual savings depend on content—image-heavy scans compress dramatically, while text-only PDFs see minimal reduction since text is already compact.

Does PDF compression reduce quality?

Compression reduces image quality proportionally to the compression level chosen. Text and vector graphics (charts, diagrams, logos) remain perfectly sharp at any level. For documents with important photos, choose Maximum or High quality to maintain visual clarity.

What's the best compression level for email?

High Quality (70% image quality) is recommended for most email attachments. It typically reduces file size by ~35% while maintaining good readability. For documents with detailed images, use Maximum Quality. For text-heavy documents, Medium Quality works well.

Can I preview compression before saving?

Yes, ScanLens shows the estimated file size before and after compression. You see exactly how much space you'll save before applying any changes. If the reduction isn't sufficient, adjust the compression level and preview again.

Is my PDF uploaded to a server for compression?

No, all compression happens locally on your iPhone. Your documents are never uploaded to external servers. This keeps your files private and means compression works even without internet connection.