Record the original size and what must survive
Find the PDF in Finder and check its size before changing it. Note any upload limit you are trying to meet. A vague aim to make a file “as small as possible” can lead to an unnecessarily blurry result, while a specific requirement lets you stop once the document is usable and small enough.
Open the original and identify important features. Can you select text? Does it contain fillable fields, links, detailed drawings or tiny annotations? Choose a few representative pages for comparison. A large cover photograph is not a good quality test for a document whose crucial information is a table in small type.
Save the reduced version under a different filename. Keep a source copy such as report-original.pdf and a delivery copy such as report-for-upload.pdf. This also prevents you from accidentally compressing a previous compressed version when trying another setting.
Try Preview’s built-in size reduction
- Open the PDF in Preview.
- Choose File > Export.
- In the Quartz Filter menu, select Reduce File Size.
- Give the export a new filename and save it.
These are the steps in Apple’s Preview guide. Apple also documents export options for screen-optimised images, JPEG images and linearised PDFs; the options you see can depend on your macOS version. Apple cautions that compression can reduce quality and that results vary with the chosen options.
Open the saved export and compare it with the original. Do not judge only the smaller number in Finder. Look closely at the smallest useful text and at a detailed image. If the export is not an improvement for your purpose, keep the original and try a different approach.
Use PDFNest for a scanned or image-heavy document
For a scan that can remain image-based, Compress PDF offers three levels in your browser. Add the original PDF, choose Light, select Compress PDF and download the result. Compare the output before considering Recommended or Strong.
PDFNest’s current compressor renders each page into an image and puts those images into a new PDF. This happens at every level, including Light. It does not preserve selectable text, working hyperlinks, fillable fields or a searchable text layer. A visually readable result may therefore lose functionality that matters to you.
This is a more suitable choice for a bulky scan than for a small, text-based report you need to search. If your document mixes text and scanned attachments, you can process the scanned part separately and combine it with the untouched text PDF using Merge PDF. Check the combined result afterwards.
Reduce the source instead of rebuilding every page
If you created the PDF, return to the original document or presentation. Look for photos that are far larger than their displayed size, full-resolution screenshots used as tiny illustrations, and repeated background images. Reducing unnecessary image data before export can address the source of the problem.
Export another PDF from the source application and compare it. Keep text as text when the application supports it, and inspect its image-quality options rather than automatically choosing the smallest setting. For a report intended for on-screen reading, a print-focused export may contain more image detail than the reader needs, but your actual content determines what is sufficient.
If you only have the PDF, check for accidental duplicate pages or blank scans. Remove Pages can remove unwanted pages; Split PDF can extract a requested section. Do not delete required content just to meet a limit without checking the recipient’s instructions.
Compare file size, readability and features
Put the original and your candidate export side by side at the same zoom. Check small numbers, thin diagram lines, light grey text and any writing over coloured backgrounds. If the document will be printed, inspect a sample print at the size it will actually be used.
Try selecting and searching for a phrase, and test any link or field you depend on. A file that looks almost identical can behave differently after processing. For a form, the ability to type into a field may matter more than reducing the attachment by a modest amount.
If the new file is larger, do not keep it just because it came from a compression workflow. Some PDFs already store their content efficiently. Rebuilding their pages can add more data than it removes. Use the version that satisfies the requirement while preserving the content and features you need.
If the PDF is still too large
Read the actual limit shown by the upload form or recipient. Check whether it applies to one attachment or the combined set. A file displayed as a rounded value in Finder can still be slightly above a strict byte limit, so leave some room instead of aiming for the exact boundary.
If a readable version will not fit, ask whether separate parts or another delivery method are acceptable. Dividing a document is appropriate only when the receiving workflow accepts it. A portal that requires one PDF is not helped by a ZIP archive or several fragments unless its instructions say so.
Keep the final copy clearly labelled and reopen it from the place you plan to attach it. For more detailed diagnosis of softness and lost text selection, see why a PDF becomes blurry after compression. The best result is a usable file under the relevant limit, not the largest percentage reduction.
Open Compress PDFProcess files in your browser, then check your download.
Open Compress PDF →Frequently asked questions
Can I reduce a PDF without installing software on my Mac?
Yes. Try Preview’s export filter, or use PDFNest in your browser for image-based compression when that fits the document.
Is Reduce File Size guaranteed to produce a smaller file?
No. Results depend on the original PDF and the export settings. Compare the saved file with the original.
Does PDFNest Light compression keep searchable text?
No. It preserves more visual detail than the stronger levels but still rebuilds every page as an image.