"You can sometimes reduce the file size of a PDF simply by using the Save As Other command. Reducing the size of PDFs improves their performance—particularly when they’re being opened on the web—without altering their appearance.
The Reduce File Size command resamples and recompresses images, removes embedded Base-14 fonts, and subset-embeds fonts that were left embedded. It also compresses document structure and cleans up elements such as invalid bookmarks. If the file size is already as small as possible, this command has no effect.
Note: Reducing the file size of a digitally signed document removes the signature."
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If you are on Mac
Here are the steps:
Open the PDF in the Preview app on your Mac,
Choose File > Export.
Click the "Quartz Filter" pop-up menu, then choose "Reduce File Size".
Mac Source: https://support.apple.com/guide/preview/compress-a-pdf-prvw1509/mac
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If you are on PC
Here are the steps:
If you do not have PDF editing software, get Adobe Acrobat Reader DC here: https://get.adobe.com/reader/ (for free, of course🤑)
Open the PDF in your PDF editing software (ex. Adobe Acrobat Reader DC)
Choose File > Save As Other > Reduced Size PDF.
For the version compatibility: "Retain Existing"
Click "Ok" and save the file
PC Source: https://helpx.adobe.com/acrobat/using/saving-pdfs.html#reduce_file_size_by_saving
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For example, here's a pdf reduced from 14.1MB to 0.0245MB 😊
(That's a 98% size reduction and still the same looking quality!)