author avatar
    Senior Product Manager
 

Summary
Discover efficient methods to reduce the size of large PDF files for email attachments with our detailed guide, covering a range of PDF compression software and online techniques.



I. Why do you need to compress PDF files

how to compress pdf
PDF is the most popular file format for sharing information in the Internet age. It is convenient to open on both computers and mobile phones. However, large PDF files may encounter transfer obstacles. To efficiently compress PDF files, professional compression software is required.
Each PDF file will contain a complete description of the fixed layout, including text, fonts, graphics, and other information. Image data occupies more memory compared to text data. The file size will increase significantly if multiple or high-quality images are included in the PDF file.
Common reasons for oversized PDF files:

● The file contains multiple high-quality images.

● Files (vector images) exported from Adobe Illustrator.

● Contains multi-page documents (such as Word or PowerPoint, etc.).

TipsTo check the size of a PDF document using Adobe Acrobat Pro, go to View > Show/Hide > Navigation Panes > Contents, then select “Statistics Space Usage” from the Options menu. Alternatively, right-click the PDF file in the folder and click Properties.
Avoid creating large PDF files by not using a scanner. Instead, save scanned documents in PDF format and convert them to editable documents using OCR technology to reduce file size.
There are various methods of PDF compression, including reducing image size through format conversion and deleting unnecessary file information. Multiple PDF compression software and methods will be introduced to help quickly compress PDF to a suitable size.

II. Introduction to Professional PDF Compression Software and Operation

1. Renee PDF Aide

To address the issue of an oversized PDF file, use Renee PDF Aide for file compression. Its “Optimize” feature offers three compression options for quick file reduction. Beyond compression, the software enables editing and converting PDFs to formats like Word, Excel, PowerPoint, EPUB, Image, HTML, and TXT, processing up to 80 pages per minute. It also converts scanned PDFs and image text into editable text, supporting one-click batch conversion.
Hot Topic - ADsRenee PDF Aide - Powerful PDF Editing Tool

Easy to use Friendly to computer beginners

Multifunctional Encrypt/decrypt/split/merge/add watermark

Safe Protect PDF with AES256 algorithms

Quick Edit/convert dozens of PDF files in batch

Compatible Convert PDF to Excel/PowerPoint/Text, etc.

Easy Use with simple steps

Functional Encrypt/decrypt/split/merge/watermark

Safe Protect PDF with AES256 algorithms

Free TrialFree TrialNow 800 people have obtained the free version!
The specific operation steps are as follows:
① After opening the software, click “PDF Tools“.
select pdf tools in renee pdf converter
② Click “Optimize” > “Add File” to import the PDF file.
optimize pdf file with renee pdf aide
③ Select optimization options:
● Online page loading speed (linearize): This optimization option is suitable for webpage PDFs, and the loading will be smoother after optimization.
● Compress images: Compress images in PDF files.
● Compress data stream: compress pdf file data stream. (PDF file capacity becomes smaller)
④ Finally, click “Convert”.

2. Adobe Acrobat Pro

Adobe Acrobat Pro offers various settings to reduce PDF file size, including default options that remove embedded fonts, compress images, and eliminate unnecessary items. It is recommended to analyze file space usage before optimization to determine how to minimize the file effectively. While Adobe Acrobat Pro provides effective compression, it is a paid software and may not be suitable for personal use. Consider using Renee PDF Aide as an alternative.
a. One-click compression of PDF files
The specific operation steps are as follows:
① Open the PDF file to be compressed in Adobe Acrobat Pro.
② Click “File” > “Save As Other” > “Reduced Size PDF”.
adobe Reduce PDF size
③ Select a location to save the file, and click “Save”. After the compression is complete, the software will prompt a message showing the compressed size of the PDF file.
b. Compress PDF files using advanced options
The specific operation steps are as follows:
① Open the PDF file to be compressed in Adobe Acrobat Pro. Click “File” > “Save As Other” > “Optimized PDF” to open the “PDF Optimizer” dialog box.
② To use the default settings, select “Standard” from the “Settings” menu. Or set according to your own needs, and then click “OK”.
Note: If you change any settings in the PDF Optimizer dialog, the Settings menu will automatically switch to Custom. Once you have selected options, click OK.
optimize pdf
③ In the “Save Optimized File As” dialog box, click “Save” to overwrite the original PDF with the optimized PDF, or save it in a new location with a new name.

3. Reduce PDF Size

Reduce PDF Size is a free software for compressing PDF documents. Its interface is simple and user-friendly, allowing even novices to quickly complete the compression process. The software supports batch conversion of PDF files, enabling users to compress multiple files simultaneously. With five different compression settings available, users can choose the compression ratio that best suits their requirements. Please note that Reduce PDF Size is solely a PDF compression software and does not offer additional PDF functions.
Click “Option” to select the compression settings, the software supports the following PDF compression settings:

● Screen-view-only: Low resolution, 72 dpi images.

● Low Quality (eBook): medium resolution, low quality, 150 dpi image.

● High Quality (Printer): High quality, 300 dpi image.

● High Quality (Prepress): high quality, color preservation, 300 dpi image.

● Default Quality: The default quality, the output file may be larger.

The compression operation of this software is very simple, and the specific operation steps are as follows:
① Click “File” > “Add PDF Files” in the menu bar to import the PDF file to be compressed.
Add PDF file
② In “Option”, select the compression setting.
PDF Compression Settings
③ Click “File” > “Reduce PDF File Size” to select the output location of the PDF file. Finally, just wait for the file compression to complete. You need to pay attention that the compressed PDF file will be saved in the output folder, and the source PDF document will not be modified.
Reduce PDF size

4. Preview (macOS)

Mac users can compress PDF files without downloading software by using the built-in “Preview” application. Simply drag the PDF file into the software and reduce its size through the “Quartz filter” function. Note that the quality of the PDF may decrease after compression.
The specific operation steps are as follows:
① In the “Preview” program on Mac, open the PDF file to be compressed.
② Then click “File” > “Export”.
preview export
③ Click “Quartz Filter” and select “Reduce File Size” in the pop-up menu. Finally, tap “Save.”
quartz filter
Comparison of four compression software:
Renee PDF Aide Adobe acrobat pro Reduce PDF Size preview (macOS)
compatibility Windows Windows/ Mac Windows Mac
price free trial costly free free
easy to use
safety
compression efficiency Three more compression modes are optional A variety of compression settings are optional/ and the compression requirements can be customized Five compression modes/ different compression rates are optional The compression effect is average/ and the compression efficiency cannot be selected
PDF editing function Convert/ Split/ Merge/ Delete/ Select and Add Watermark Add/ delete and modify PDF text and images x Extract single pages/ page sorting/ tagging
PDF conversion function x x
Summarize

Based on the above function introduction and comparison, Renee PDF Aide has the highest comprehensive score among the four compression software, especially for personal use. This software can not only provide PDF compression function, but also provide comprehensive PDF editing and conversion functions. Download it to meet your various PDF usage needs in daily life or work.

III. How to compress PDF files online

If you do not have high requirements on the compression rate and quality of the software, you can also use the online PDF compression method described below. The great thing about using an online PDF compressor is that you don’t need to download software to use it. However, if the PDF file is too large or a private file, it is not recommended to use the online compression method.

1. SmallPDF

Quickly compress large PDF files up to 5GB with SmallPDF. Supports compressing scanned PDF files to 144 DPI for easy uploading and emailing. Browser-based tool works on any operating system. Also offers PDF conversion, editing, and merging. Registration required for 14 days of free use.
SmallPDF online compression link: https://smallpdf.com/compress-pdf
online compression tool

2. Online2PDF

Online2PDF is a free online PDF compression tool with a 100MB size limit for files. Users can upload and compress up to 20 files simultaneously, with three image compression settings available. These settings include image quality, resolution, and color/black and white options to reduce PDF file size. Online2PDF also offers various editing functions like PDF conversion, merging, editing, decryption, and page management.
Online2PDF online compression link: https://online2pdf.com/pdf-reduce-size
Compress PDF Online

3. PDFresizer

Use the PDFresizer tool to optimize and compress large PDF files for free. This online tool offers various compression options such as optimize, convert, split, crop, and adjust page resolution. For further size reduction, try the “Resize PDF” function with four page resolution options and paper size settings. The website allows uploading files up to 100MB, supports batch uploading, and can compress up to 50 files simultaneously.
PDFresizer online compression link: https://pdfresizer.com/optimize
PDF compression tool

4. DocuPub

For more control over PDF compression quality, use DocuPub’s online tool. It allows you to change page sizes and limit zoom ratios. Choose preset sizes or customize. File size must be under 20MB for compression. No batch compression, only one PDF at a time.
PDF file compression
Hot Topic - ADsRenee PDF Aide - Powerful PDF Editing Tool

Easy to use Friendly to computer beginners

Multifunctional Encrypt/decrypt/split/merge/add watermark

Safe Protect PDF with AES256 algorithms

Quick Edit/convert dozens of PDF files in batch

Compatible Convert PDF to Excel/PowerPoint/Text, etc.

Easy Use with simple steps

Functional Encrypt/decrypt/split/merge/watermark

Safe Protect PDF with AES256 algorithms

Free TrialFree TrialNow 800 people have obtained the free version!

IV. Other PDF compression methods

In addition to the above-mentioned PDF compression software and PDF online compression tool, the following will introduce two other compression methods, which can effectively reduce the size of PDF documents.

1. Compress file size when creating PDF

If you used Word to create the PDF document, you can reduce the file size when saving the document. In Word, to save a Word document as a PDF, you need to click the “Save As” option to convert it. If you find that the PDF document after saving as is still too large, you can use another option in Word to compress its file size.
The specific operation steps are as follows:
① Open the Word document to be converted to PDF, click the “File” > “Save As” button, and then select the location to save the file.
② In the pop-up Save As window, enter the file name and select the save type “PDF (*.pdf)”. In “Optimize for” at the bottom of the window, select “Choose the smallest file size (publishing online)”. Finally, click “Save”.
word save as pdf

2. Batch compress PDF files via ZIP

Now people often use ZIP to compress and send large files, which solves the problem of difficulty in sending large files. Microsoft has used ZIP for file compression since 1998, and there is built-in compression in the Windows operating system.
If you are working with multiple PDF files and need to compress a large number of PDF files, you can organize them into a folder and ZIP the entire folder so that you don’t need to compress each file individually. By compressing PDF files through ZIP, you can get a good compression effect without losing any data, and it also supports password-protected compressed files. ZIP files use lossless compression to ensure quality, so the quality of the files in the ZIP files will not change after compression. However, it should be noted that since the ZIP file itself has the risk of accidental damage, once some data is damaged, the rest of the documents in the file may be affected.
On a Windows computer, you can right-click the folder you want to zip, then choose Send To > Compressed (zipped) Folder.
zip compression
Summarize
When compressing PDF files, it is recommended to use professional software like Renee PDF Aide for better results in terms of compression effect, speed, and versatility.