[Mac/Windows] Heavy PDF File Size! Easy Ways to Compress and Reduce File Size for Free

PDF files are commonly used in both work and private life. However, if they contain many images or span multiple pages, the file size can swell to dozens of MBs. You might have experienced panic when exceeding the standard business email attachment limit (typically around 2MB to 10MB) and being unable to send your mail.

Most of the reasons why PDFs get heavy lie in high-resolution images embedded in the file or font data. In this article, we explain the concrete steps to safely compress PDF file sizes using Mac or Windows standard features, or free web services, without using special paid software.

Main Reasons Why PDF Files Get Heavy

Knowing why PDFs get heavy before learning how to fix it will help prevent it when creating documents.

  • Embedded high-resolution images:If you paste high-quality photos taken with a camera or smartphone directly and convert them to PDF, they will be saved at that original quality, making the file size extremely large.
  • Embedded fonts (characters):To display the same font on any device, if the settings are set to embed the entire font data in the PDF, the size will increase even if the file is mostly text.
  • Residual editing data:For PDFs created with software like Illustrator, information for re-editing in the original program (such as layer structure) may be retained within the file.

[For Mac Users] Compress Using Built-in "Preview"

If you are using a Mac, you can compress PDFs without installing any additional apps using the built-in "Preview" app.

  1. Open the PDF file you want to compress in the "Preview" app.
  2. Click "File" > "Export..." in the menu bar.
  3. A settings window will open; from the "Quartz Filter" dropdown menu, select:"Reduce File Size"to apply it.
  4. Click "Save" to export the newly compressed PDF.

*Note: Although this method is very easy, the output image quality can become quite rough. Especially for PDFs containing small text or drawings, make sure to open the file after saving to check if it remains legible.

[For Windows Users] Compress and Save Using Microsoft Word

On Windows, it is difficult to compress files using only PDF readers, but if you have Microsoft Office (Word) installed, you can use the following workaround.

  1. Launch Word and open the PDF file you want to compress (if a dialog box about converting PDF to a Word document appears, click "OK").
  2. Select "File" > "Save As".
  3. Set the file type to "PDF (*.pdf)".
  4. In the optimization options displayed within the settings, select:"Minimum size (publishing online)"to apply it.
  5. and click "Save".

Word will automatically resize the images in the PDF to an appropriate resolution, allowing you to reduce the file size with minimal layout disruption.

Using Free Online Compression Tools (With Caveats)

If standard OS features do not work well or you want stronger compression, using free web services like "iLovePDF", "Smallpdf", or "Adobe Acrobat online tools" is also an option. Simply drag and drop the PDF onto the browser, and it will generate an optimized PDF in seconds.

[Security Warning!]
Although these online tools are extremely convenient, they transmit your uploaded files to external servers, even if only temporarily. Therefore:Never upload important or sensitive documents that must not be leaked, such as personal information, corporate secrets, contracts, or unreleased project materials.It is safe to limit their use to compressing publicly shareable brochures or general reference materials.

Use "FS!QR" to Send Heavy Compressed Files or Sensitive Data Safely

If "it still exceeds the email attachment limit despite compression" or "you do not want to use external online tools due to sensitive information", instead of email attachment, the best method is to:"Secure file-sharing link"generate and send a secure file-sharing link.

free file sharing service「FS!QR」With a free file-sharing service, you can upload your PDF via drag-and-drop on your browser to instantly generate a download URL or QR code for the recipient.

FS!QR allows you to protect uploaded files with a password (passphrase), preventing misdelivery to third parties or interception. Furthermore, since the data is automatically and completely deleted from the server after the set period expires, there is no security risk of "sent files remaining on the internet forever". Please utilize FS!QR for sending heavy PDFs that cannot be attached to emails, or for exchanging business documents where security is highly valued.

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