How to Reduce PDF File Size on Mac Using Preview
Learn how to shrink a PDF on a Mac with Preview's Reduce File Size filter while protecting readability and image quality.
How to Reduce PDF File Size on Mac Using Preview (Quick Answer)
Open the PDF in Preview, choose File, then Export, and select Reduce File Size from the Quartz Filter menu.
Save the compressed PDF under a new filename and compare its quality and size with the original.
Preview’s standard filter can compress images heavily, so it is best for screen viewing and email rather than documents that require high-quality printing.
Keep the Original PDF
Duplicate the original before compressing it. Preview may reduce image resolution and quality in ways that cannot be reversed.
Use a descriptive filename such as report-compressed.pdf so the high-quality master remains easy to identify.
Compress the PDF in Preview
The usual process is:
- Open the PDF in Preview.
- Select File and then Export.
- Choose PDF as the output format.
- Open the Quartz Filter menu.
- Select Reduce File Size.
- Enter a new filename.
- Select Save.
Menu labels can differ slightly between macOS versions.
Check the Compressed Result
Do not judge the result by file size alone. Open the new PDF and inspect:
- Small text
- Photographs
- Charts and diagrams
- Signatures
- Fine lines
- Scanned pages
Also check the document at normal zoom and in print preview. A very small PDF is not useful if important details are unreadable.
Why Preview Can Reduce Quality So Much
Preview’s built-in filter may downsample and recompress images throughout the document. This can create:
- Blurry scans
- Blocky photographs
- Faint text
- Rough diagrams
- Unreadable annotations
Digitally created text often remains sharp, while image-based pages are more visibly affected.
Other Ways to Make the PDF Smaller
If the Preview result is too aggressive, try:
- Removing unnecessary pages
- Exporting again from the source document
- Reducing source image dimensions
- Using a PDF compressor with adjustable quality
- Splitting the PDF into smaller files
- Sharing a secure cloud link instead of attaching it
Adjustable compression provides more control than Preview’s single standard filter.
Understand What May Change
Exporting or processing a PDF can affect interactive features such as forms, comments, layers, links, accessibility tags, or digital signatures.
Check these features after compression. Do not overwrite a signed or certified original.
Frequently Asked Questions
Why did Preview make my PDF blurry?
The Reduce File Size filter lowers image quality to achieve a smaller file. Use the original or a less aggressive compression tool when clarity matters.
Can I choose the compression quality in Preview?
The standard Preview workflow provides limited control. A dedicated PDF compressor may offer image resolution and quality settings.
Why is the compressed PDF not much smaller?
The file may contain mostly text and vector graphics, or its images may already be compressed.
Does Preview compression remove pages or text?
It should not intentionally remove them, but always review the output because damaged files and complex features can behave unexpectedly.