PDF file usually comes with lots of graphics and images, which may make PDF file size quite large. While, large PDFs often bring troubles when we uploading or sending PDFs by email which has size limit, or the large file eat up too much space on our Mac. In this case, reducing PDF file size on Mac while without losing quality becomes a crucial thing.
To reduce PDF file size on Mac, we can use Preview, free online sites, free PDF Compressor, and paid software. Here in this article we will introduce and compare all the available choice. We know, most of you are worried that reducing the size of the PDF will also reduce the image quality, which makes the PDF unreadable. So we will also introduce specialized software that can compress PDF without reducing the image quality.
To help you find which available options works best at reducing PDF file size, we tested 6 PDF compressor tools using three different PDF files each with different size and content. You’ll see how all the tools perform in each scenario — and find out the strengths and weaknesses of each one.
① Number 1 test PDF: A 4.6 MB sized PDF that have 543 pages and are mostly text based, have no images.
② Number 2 test PDF: A 3.6 MB sized PDF that have 60 pages and its content both have images and text.
③ Number 3 test PDF: A 55.1 MB sized PDF that have 23 pages and it's content are mostly images.
Cisdem PDF Compressor
Free Download macOS 10.15 or later 
Free Download Windows 11/10/8/7
We categorized emails and comments send from our readers. In most cases they looking for a PDF compressor when they need to upload a PDF file or sending them via email. They know that there are online sites that can help compress the size of PDF file but for privacy and security they prefer an offline option that can compress PDF Files in batches, and to ensure that the recipient can see the document clearly they showed more interest on tools that keep the same PDF quality with less file size.
The easiest option, which can reduce the size of large PDF files by more than half without reducing image quality is Cisdem PDF Compressor for Mac.
Simple steps to reduce PDF file size on Mac without losing quality:
Free Download macOS 10.15 or later 
Also, you can check the tutorial video of reducing PDF file size on Mac:
Tools to compress a PDF file on Mac are plentiful enough, and choosing the best is really not easy. While, the reasons why Cisdem PDF Compressor comes as the best choice is not only due to its high quality compression, but also for a set of benefits it offers to users.
Also, as it is a offline PDF compressor there is no need to worry about information leakage.
① Number 1 test PDF: All the 3 modes take less than 10 seconds.
② Number 2 test PDF: All the 3 modes take less than 10 seconds.
③ Number 3 test PDF: All the 3 modes take less than 20 seconds.
Number 1 test PDF:
Small File Size Mode: 4.6MB - 3.9MB
Medium File Size Mode: 4.6MB - 3.9MB
Large File Size Mode: 4.6MB - 3.9MB
Number 2 test PDF:
Small File Size Mode: 3.6MB - 962.67KB
Medium File Size Mode: 3.6MB - 1.47MB
Large File Size Mode: 3.6MB - 3.31MB
Number 3 test PDF:
Small File Size Mode: 55.1MB - 6.03MB
Medium File Size Mode: 55.1MB - 15.2MB
Large File Size Mode: 55.1MB - 40.91MB
① Number 1 test PDF: All 3 modes gives the same results, nearly no image quality loss.
② Number 2 test PDF: The quality of text stay the same in 3 modes. For images "Large File Size" and "Medium File Size" modes gives almost the same results as the original quality, the picture quality of small size mode is obviously reduced.
③Number 3 test PDF: The "Large File Size" and "Medium File Size" modes gives almost the same results as the original quality, the picture quality of small size mode is obviously reduced.
Picture quality comparison of the 3 modes
See none of them showed any difference in quality from the original quality.
We all know, Adobe is leading in offering solutions to manage PDFs, its PDF editor, the Adobe Acrobat series is super powerful to handle all kinds of PDF files, including reducing PDF file size on mac with good quality.
One of my friends once asked me if Adobe Reader can reduce pdf file size on Mac, the answer is NO.
Adobe Reader is a free PDF viewer open to everyone from Adobe, it allows users to view, highlight, add notes, print, fill and sign PDF. But if you need advanced features, such as editing, creating, exporting, compressing, etc., you will have to subscribe its Acrobat version.
Under Reduce File Size choose single file.
Choose the location to save the smaller size PDF. you can choose to save it to your computer, adobe cloud or other file storage.
tips: You can click advanced optimization to optimize the PDF size as standard or for mobile, and you can choose to only reduce image size in the PDF.
①Time takes for compression:
Number 1 test PDF: Take less than 30 seconds.
Number 2 test PDF: Takes more than 2 minutes.
Number 3 test PDF: Take less than 30 seconds.
Number 1 test PDF:
Adobe standard Mode: 4.6MB - 3.9MB
Adobe mobile Mode: 4.6MB - 3.9MB
Number 2 test PDF:
Adobe standard Mode: 3.6MB - 1.1MB
Adobe mobile Mode: 3.6MB - 2.38MB
Number 3 test PDF:
Adobe standard Mode: 55.1MB - 11.9MB
Adobe mobile Mode: 55.1MB - 16.24MB
Number 1 test PDF: All 2 modes gives the same results, nearly no quality loss.
Number 2 test PDF: The quality of text stay the same in 2 modes. For images you'll see image quality degree in "mobile Compression”. While for the standard mode it gives the same quality of the original PDF.
Number 3 test PDF: You'll see image quality degree greatly in mobile mode, the standard mode gives almost the same quality.
A Mac is designed to boost productivity both in life and work, so it is quite reasonable that some powerful applications comes with MacOS for totally free. Among these apps, there are 2 Mac tools can reduce PDF file size on Mac for free. One is Preview, while the other one is Colorsync.
Preview is the free Mac program developed to view and manage PDFs or images. With 3 steps, Preview can get your PDF file size reduced.
①Time takes for compression:
Number 1 test PDF: 25 seconds.
Number 2 test PDF: 13 seconds.
Number 3 test PDF: 37 seconds.
Number 1 test PDF: 4.6MB - 10.3MB
Number 2 test PDF: 3.6MB - 3.2MB
Number 3 test PDF: 55.1MB - 63.6MB
You see, In our test, the largest downside of using preview to compress PDF on Mac is, it will always increase the size of PDF file, instead of compress it.
What surprise us is that although it increased the size of the PDF file, but it also lowered the quality of the output PDF file.
Disadvantages:
Another Mac tool to compress PDF is ColorSync, it is a color management system, helping users to modify an image by adding effect, tweaking color space, adjusting colors or brightness, etc.
In our test, it gives almost the same result as preview.
Disadvantages:
If these 2 solutions don't help, have a try on the best PDF Compressor for Mac.
Most online PDF compressors are free, which makes them the most affordable way to compress PDF on Mac. However, in the case of large PDF files, you need to upload and download them, so it may take a long time to process. Also, there are many sites online that claim to be able to compress PDFs, but you should be careful as some sites have a lot of advertisements but are not very effective. If the site is suspicious, you may be worried about information being leaked.
If you want to reduce PDF file size on Mac without losing quality online, you’d better use following 2 online tools.
After testing all the online PDF compressors ranked in the top 2 pages of Google results, PDFCompressor finally comes as my favorite online choice. It can compress a PDF file as small as possible, also reduce the file size without losing original quality. Even, it supports to reduce a single or multiple PDFs in batch.
In my test of compressing a 4.4MB-PDF file, PDFCompressor helps to reduce the file size to 635kb, while the quality is not lost, such as its layout, image resolution are not sacrificed.
Follow the steps to reduce PDF file size on mac online
Cons:
①Time takes for compression:
Number 1 test PDF: 25 seconds.
Number 2 test PDF: 13 seconds.
Number 3 test PDF: 37 seconds.
Number 1 test PDF: 4.6MB - 3.9MB
Number 2 test PDF: 3.6MB - 1.8MB
Number 3 test PDF: 55.1MB - 28.7MB
Reducing the file size also reduces the image quality. This is what this online site will show you, you will see files which are largely text will keep the quality but for files with a lot of images the quality will also reduced, and some even unusable.
When it comes to online PDF compressor, the most popular is Smallpdf.com. It is the platform enjoys large popularity to provide various online PDF services. You can upload single PDF for compression from local, GoogleDrive or Dropbox.
However, Smallpdf also has some shortcomings. For example, you need to bear the advertisements on the screen, and you cannot compress PDF files in batch. Also, a defaulted mode is set for users. For instance, a PDF file in 1.77MB will be compressed to 716.27KB.
Follow the steps to compress PDF on Mac Online
Cons:
①Time takes for compression:
Number 1 test PDF: In our test this online sites shows that the first PDF is already pretty compressed.
Number 2 test PDF: 19 seconds.
Number 3 test PDF: 59 seconds.
Number 1 test PDF: Failed
Number 2 test PDF: 3.6MB - 1.5MB
Number 3 test PDF: 55.1MB - 14.9MB
The online site don't support compressing PDF files that are mainly text and the output quality is merely satisfactory, with some images turn out blurred.
As there are lots of online free PDF compressors available, you may want to try others for a wiser decision. No need to do this yourself, we have done a review of several top online pdf compressor for your consideration.
An extended way to reduce PDF file size on Mac is using command line. Here we need to use Ghostscript, a standalone command line application and interpreter for the PostScript language and PDF documents. Ghostscript’s standpoints include file compression, file conversion with OCR technology, color management, printing, etc. Now, follow our steps and try this way if you are not new to the command line.
If you are not intended to reduce pdf file size with a software or online service, here are some small tips to compress pdf for you.
Ensure image quality: Presenting high-quality images and texts can give a more engaging experience for the recipient. After you compress the size of PDF file, double-check to ensure they still look clearly.
If you only need to compress 1 or 2 PDFs, I recommend using the standard Mac app or a free online site, especially if your file is small. If you often need to work with PDFs, or if you want to compress PDF company documents or PDFs with personal information, we recommend using specialized software.
If you don't mind the high cost, the best option is to use Adobe Acrobat, but if you want a more efficient way to reduce PDF files on your Mac and want a convenient and affordable option, Cisdem PDF Compressor is recommended.
Free Download macOS 10.15 or later Free Download Windows 11/10/8/7
Carolyn has always been passionate about reading and writing, so she joined Cisdem as an editor as soon as she graduated from university. She focuses on writing how-to articles about PDF editing and conversion.
Henry B
I also got huge frustration from large size PDFs, I tried to compress in Adobe, but still too large to be viewed by our office software. Until I tried your method 2 and 3, and I personally recommend method 2, though you have to pay for it, it saves work.