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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.
Download on the App Store

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

PDF compression can reduce file size by re-encoding page images at a lower quality or resolution. The result depends on the source: an image-heavy scan may shrink, but an already compact PDF may stay the same size or become larger. ScanLens processes the export on your iPhone; check the saved copy rather than assuming a fixed reduction.

Use compression when the pages are correct but the file is too large to email or upload.

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.

You can also sign the PDF or add password protection before sending the smaller copy through email or a cloud destination.

How to reduce PDF file size on iPhone, step by step

  1. Open or import the PDF. Use the scan in your ScanLens library, or import a PDF saved in Files.
  2. Open the export options. Keep PDF as the format and compare the estimated sizes for the available quality levels.
  3. Start with a small quality reduction. Step down only as far as the email or upload limit requires.
  4. Save a separate copy. Check its actual size in Files by touching and holding the PDF and choosing Get Info.
  5. Reopen the copy. Zoom in on small print, signatures, and tables before sending it. Keep the original for another export.

Reduce the size of a PDF scanned in Notes or Files

For a Notes scan, open the scanned attachment inside the note, use Share, and choose Save to Files. A scan made in Files is already a PDF in the folder where you saved it. Import that PDF into ScanLens and follow the export steps above; you do not need to scan the paper again.

Compression runs on your iPhone without uploading the PDF to a compression server. Email or cloud sharing sends the exported copy through that service and may need an internet connection. If a readable copy is still too large, see three ways to handle a PDF too big to email.

How PDF compression affects readability

Compression can re-encode page images at a lower quality and reduce their pixel dimensions. This may lower the file size, but even a modest reduction can soften small text, signatures, thin table lines, or photographs.

This image compression is lossy: removed detail cannot be restored from the smaller copy. Choose the lightest setting that meets the attachment or upload limit, then inspect the exported PDF.

Why you should keep the original PDF

Compression cannot improve a blurry scan. Save a separate export and keep the original PDF for printing, archiving, or another export at higher quality.

ScanLens exports a copy and keeps the source document in the library. Re-export from that source if the smaller copy loses details you need.

A text-based PDF may already be compact. Rebuilding its pages as images can increase the file size and remove selectable text or vector content. Compare the actual exported size and check text selection or search if your workflow needs them; keep the original when the new copy offers no benefit.

Compression Levels

Which PDF compression level should you choose?

Compare these quality levels for the same scanned document and export options. They describe a relative tradeoff, not a measured reduction from your original PDF. Check the saved size and readability.

LevelImage qualityRelative file sizeBest for
MaximumHighestLargestKeep more detail for print, photographs, stamps, signatures, and small type.
HighHighSmallerStart here for email or uploads, then compare the actual size with the sender, recipient, or portal limit.
MediumBalancedSmaller stillTry when High is still too large; check small text, signatures, and tables in the exported copy.
LowLowestSmallestUse only if the result remains readable. Keep the original; use a link or split the PDF if no readable setting meets the limit.
Send Limits

What to check before sending or uploading a PDF

Choose a target size based on the recipient’s requirements. Check the saved PDF, the combined size of all attachments, and the upload portal’s rules. For delivery options, see too-big-to-email guide.

Sending methodWhat to checkNext step
Email attachmentBoth sender and recipient attachment or message-size limitsCompare the saved PDF and all other attachments with both limits.
Several attachmentsThe total message limit, not only each fileSend fewer files if the recipient accepts separate messages.
Cloud linkRecipient access, sign-in requirements, and link expirySet the intended permissions and confirm the recipient can open the link.
Workplace emailOrganisation policies for attachments and external linksUse the approved channel or ask the administrator for the current rules.
Upload portalAllowed file size, PDF format, and document requirementsCheck the exported copy; split only if the portal accepts multiple files.

If no readable export meets the limit, keep the original and share an accessible cloud link or split the PDF when the recipient accepts multiple files. Do not remove required pages just to meet a size limit.

Frequently Asked Questions

Why is my PDF bigger after compression?

Text-based or already optimized PDFs can grow when their pages are exported as images. Compare the saved copy with the original in Files. If the copy is larger, use the original instead of compressing that copy again.

How can I get my PDF under an upload limit?

Lower the export quality one step at a time and check the saved size. If text becomes unreadable, split the original only if the portal accepts multiple files. When one file is required, ask the recipient for another delivery method instead of removing required pages.

Why can’t I select or search text in the compressed PDF?

Exporting can turn text-based pages into images. Use the original if you need its selectable text. OCR search in the ScanLens library does not establish that the exported PDF has a searchable text layer; test the saved copy in your PDF reader.

What should I do if small print looks blurry after export?

Export again from the original at a higher quality. Detail removed by compression cannot be recovered from the smaller copy. Strong compression can also reduce OCR accuracy: use the original for recognition when possible and check names and numbers in the extracted text.

Related Topics

📑

Merge PDF

Combine PDFs before compressing.

 🔀

Reorder PDF Pages

Drag thumbnails to change page sequence.

 🔄

Rotate PDF on iPhone

Fix sideways pages before sharing the compressed file.

 ✉️

Scan and Email a Document

Prepare a readable attachment and send the finished PDF from iPhone.
Reduce File Sizes

Ready to Compress PDFs on iPhone?

ScanLens is a free app. Choose a quality level, compare the export size, and check the saved PDF before sharing. Keep the original for another export.

Download on the App Store