For a one-off PDF, start with Preview: it can reduce file size on Mac, and Apple documents a built-in export-and-compress workflow in Preview on iPhone with iOS 26. Choose Acrobat for advanced desktop controls or batch work, PDF Expert for a broader Apple-device PDF suite, PDFgear for a dedicated alternative with offline app options, or PDF Squeezer for compression presets and batch processing. Compression can soften images or affect interactive content, so keep the original and check the exported file before sending it. For confidential documents, use an installed tool rather than uploading the PDF to a browser compressor.
Which PDF compressor should you choose?
| Tool | iPhone | Mac | Offline workflow | Batch compression | Best fit | Main trade-off |
|---|---|---|---|---|---|---|
| Apple Preview | Yes, the documented export workflow is for iOS 26 | Yes | Yes, in the installed app | Not stated by Apple for these workflows | Free, occasional compression without installing another app | Fewer documented quality controls than a dedicated optimizer |
| Adobe Acrobat | Yes; mobile compression requires a subscription, according to Adobe | Yes | Desktop workflow; web workflow uploads to Adobe cloud storage | Yes, desktop instructions include multiple files | Advanced optimization, multiple compression levels, and professional PDF workflows | Advanced desktop optimization requires Acrobat Pro, Premium, or Studio; web processing is cloud-based |
| PDF Expert | Yes | Yes | Installed apps offer a local workflow | Not stated in the cited feature pages | Compression alongside editing, signing, conversion, and page management | Some features may require payment; current plan entitlements vary |
| PDFgear | Yes | Yes | Vendor offers offline compression through installed apps | Promoted by the vendor | A dedicated editor and compressor with offline app options | Its “up to 90%” reduction figure is a vendor claim, not a typical or independently verified result |
| PDF Squeezer | iPhone and iPad versions are listed in the App Store | Yes | Installed app workflow | Promoted by the App Store listing | Compression presets, preview, and batch work | More focused on compression than full PDF management |
| Acrobat on the web | Browser-based | Browser-based | No; the documented workflow saves the result to Adobe cloud storage | Adobe’s web instructions include an Add files option | Quick compression when uploading the document is acceptable | Requires upload and download; Adobe documents a 2 GB web compression limit |
These are use-case recommendations, not a universal file-size ranking. The result depends on the source PDF: image-heavy scans can often shrink substantially, while text-heavy or already-optimized files may change very little.
Compress a PDF on Mac with Preview
Preview is the simplest free starting point on a Mac. Apple warns that using its Reduce File Size filter can lower quality, and the resulting size and image quality vary.
- Open the PDF in Preview.
- Choose File > Export.
- Open the Quartz Filter menu and select Reduce File Size.
- Choose a new filename or destination so the original remains intact, then click Save.
- Open the exported copy and inspect its pages and interactive content before using it.
Apple also documents export options for screen-oriented output and JPEG image saving. Create Linearized PDF is intended to make a PDF load and display more quickly in a web browser; it is not the same as choosing the strongest size reduction. Optimize images for screen targets screen viewing, while saving images as JPEG uses JPEG compression and may reduce image quality. These controls are useful when the destination is known, but screen optimization may not suit printing.
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Apple’s Preview guide: Reduce the size of a PDF in Preview on Mac.
Compress a PDF on iPhone with Preview
Apple documents PDF export and file-size adjustment in Preview on iPhone running iOS 26. Do not assume the same built-in steps are available on older iOS releases.
- Open the PDF in the Preview app.
- Tap the Actions Menu beside the filename.
- Tap Export.
- Select PDF as the output format if you need to keep a PDF; Apple also lists HEIC, JPEG, JPEG-2000, PNG, and TIFF export formats.
- Adjust the file-size slider, then save or share the exported file.
After export, make sure the result is still a PDF if that is required. Test whether searchable text, links, form fields, annotations, and signatures still work: Apple’s export instructions describe the compression controls but do not guarantee preservation of every interactive feature.
Apple’s iPhone guide: Export or compress PDFs and images on iPhone.
When a dedicated PDF app is worth using
Adobe Acrobat: advanced optimization and batch processing
Acrobat is the strongest fit when Preview’s broad export filter is not enough. Adobe documents desktop compression for a single PDF or multiple files, plus advanced optimization controls for images, fonts, transparency, and compatibility. Advanced Optimization is available in Acrobat Pro, Premium, or Studio on desktop.
- Open the PDF and select All tools > Compress a PDF.
- Choose Single file or Multiple files.
- For finer control, choose Advanced Optimization, select compatibility settings, and review the Images, Fonts, and Transparency panels.
- Save the optimized PDF as a separate copy and check it before replacing or sharing the source.
Adobe’s general desktop path is documented in its PDF compression and optimization guide. For mobile, Adobe’s steps are More options > Compress PDF, followed by a High, Medium, or Low setting and Compress. Adobe says mobile compression requires an Acrobat subscription; its labels describe the trade-off as smaller size at lower quality for High compression and larger size with better quality for Low compression. See Adobe’s mobile compression instructions.
Acrobat on the web offers High, Medium, and Low compression. Its documented route is Convert > Compress a PDF, select the file and level, then choose Compress. The result uses a _compressed filename and is automatically saved to Adobe cloud storage before download. Adobe lists a 2 GB compression file-size limit for that web service; internet speed and document complexity can also affect whether conversion succeeds. See Adobe’s web compression steps and Adobe’s cloud file-size limitations.
PDF Expert: compression within a broader Apple-device workflow
PDF Expert supports compression on iPhone and iPad, as well as on Mac. Its Mac feature page lists Lossless, High, Medium, and Low document-quality choices. It is a sensible option if you also need PDF editing, conversion, signing, page organization, or annotations. If compression is all you need, Preview may be enough; do not assume every PDF Expert compression mode is included in the free tier.
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See PDF Expert’s iPhone and iPad compression guide, its Mac compression feature page, and the US App Store listing, which describes the app as free with in-app purchases and identifies iPhone, iPad, and Mac availability.
PDFgear: a dedicated alternative with offline app options
PDFgear promotes compression, editing, multiple modes, batch processing, and both online and installed-app workflows for Mac, iPhone, and iPad. Use an installed app when you want to process a file locally; its online compressor is a separate browser workflow. PDFgear advertises reductions of “up to 90%” in some circumstances, but that is the vendor’s maximum claim, not a typical result or an independent comparison. Actual savings depend on the document’s contents and prior optimization.
Check the vendor’s PDF compression page and product overview for current platform and feature details.
PDF Squeezer: compression-focused presets and batch work
PDF Squeezer is worth considering if you mainly want to shrink PDFs rather than use a full editor. Its App Store listing describes light, moderate, and strong settings, a preview before saving, batch compression, and Mac, iPhone, and iPad availability. Check the listing for current purchase terms and platform details before installing; pricing and whether versions are separate purchases are not established here.
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Choose compression based on the PDF and its destination
Scanned documents and photo-heavy PDFs
Scans and brochures often contain large embedded images, so reducing image resolution or quality can have a bigger effect than optimizing text. Start with a moderate setting and check small print, handwriting, stamps, diagrams, barcodes, and QR codes. If the text is recognized by OCR, test search and copying too: a visually readable page can still become harder for OCR to process.
Text-heavy PDFs
A digitally generated document made mostly of text and vector graphics may shrink only modestly. If compression barely changes the file, repeated lossy passes are unlikely to help and may make images worse.
Fillable forms, links, annotations, and signatures
Do not assume these survive every export or optimization method. On the compressed copy, test important form fields by entering data, saving, and reopening; follow important links; and check bookmarks and annotations. Preserve the original signed file. Compression can invalidate or remove a digital signature depending on the document and tool, so verify the specific workflow before relying on the compressed copy.
Print-ready or color-critical PDFs
Prioritize resolution, color, page dimensions, and compatibility over the smallest byte count for artwork, architectural drawings, medical images, legal exhibits, and other print-sensitive documents. A PDF that looks fine on a phone may not print well. Adobe advises checking with the print vendor before compressing a file intended for printing; see its print-quality and PDF-size guidance.
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Confidential documents
For tax, medical, identity, legal, financial, or client records, prefer an installed offline workflow unless your organization permits the service and its data handling. Preview and installed desktop apps avoid the browser-upload step described for Acrobat on the web. Do not treat a vendor’s general privacy or security language as proof that a particular workflow is approved for sensitive records.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.How to reach a file-size target without over-compressing
- Keep an untouched original. Work on a duplicate, especially for signed or fillable documents.
- Try the least aggressive useful setting. For Preview, begin with its standard Reduce File Size filter; in apps with levels, start with Medium or the default.
- Compare the actual file size. Do not assume an export made the PDF smaller. Some files are already optimized or contain mostly text and vector content.
- Inspect the result at realistic use size. Check small text, images, colors, barcodes, OCR, and print output when relevant.
- Increase compression only if the destination limit requires it. Stop when the file meets the limit rather than pursuing the smallest possible size.
- Test it in the destination workflow. Open the final copy and upload that copy to the intended site or service; a smaller byte count alone does not guarantee acceptance.
Troubleshoot common compression problems
The compressed PDF is larger
Keep the smaller, better-quality version. An already optimized PDF, a file dominated by text or vector artwork, or a change in image encoding may leave the output the same size or larger. Compare the original and exported files before choosing which to keep.
The PDF barely shrinks
The file may already be compressed, or its contents may not be suited to further reduction. Adobe says its mobile workflow cannot compress a file that is already compressed. Avoid repeated lossy compression when it produces little saving.
The file is smaller but looks poor
Return to the original and export again with a less aggressive setting or a more suitable tool. For scans, prioritize legibility and OCR; for print, prioritize resolution and check the output on paper or with the print vendor.
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A form, signature, or link no longer works
Use the original rather than relying on a broken compressed copy. Re-export using a different method and test the relevant fields, saved values, links, annotations, or signature status before distributing it.
A website still rejects the PDF
Check more than the file size: confirm the extension and page limits, whether the PDF is password-protected, whether the form structure still works, and whether the service requires searchable text or a readable barcode. Open the exported copy to rule out a damaged file, then try the destination again.
The PDF is password-protected
Some tools may require a password or may not process encrypted PDFs. Do not remove protection unless you are authorized to do so; if you are, follow the document owner’s or organization’s approved process.
Quick Recap
Quick recommendations
- Mac, free, occasional use: use Preview.
- iPhone without another app, on iOS 26: use Preview’s export slider.
- Advanced desktop controls or batch work: consider Acrobat.
- Compression plus a broader Apple-device PDF suite: consider PDF Expert.
- A dedicated alternative with offline app options: consider PDFgear.
- Compression presets, preview, and batch processing: consider PDF Squeezer.
- Confidential document: choose an installed local workflow rather than a browser compressor.
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