How can I make my PDF file size smaller without losing quality?

Open your PDF in Acrobat and go to File > Save as Other > Optimized PDF. In the 'Images' section, set color/grayscale images to about 150 dpi and monochrome to 300 dpi. Choose 'JPEG quality Medium/High' (around 85%) for images. In the 'Fonts' section, select 'Subset embedded fonts' and 'Unembed fonts' if not needed. Remove unnecessary objects and user data under 'Discard Objects' and 'Discard User Data'.

What is the difference between RGB and CMYK colors when optimizing a PDF for screen viewing?

Color Model Best Use File Size Impact. RGB (Red, Green, Blue) For on-screen viewing (websites, emails) Generally smaller file size CMYK (Cyan, Magenta, Yellow, Black) For professional printing Generally larger file size

Optimize Page Load in Adobe Acrobat — How-to & AI prompts

AI prompts

2 ways to ask · copy any one

AExecute — “help me do it”Replace the large hero image in the page PDF with a compressed export of the same image, keep…+

Replace the large hero image in the page PDF with a compressed export of the same image, keep the original as an attached file for archive, and save the optimized PDF so the page asset can load faster for slow connections.

when the reply comes backPush once: ask it to sharpen the weakest part, and to say what it assumed.

BImprove — “do it better”Before publishing, make the compression decision defensible: include both the compressed hero…+

Before publishing, make the compression decision defensible: include both the compressed hero in the main PDF and the original as an attachment, add a short note with file sizes and expected load-time improvement for mobile under 3G, and call out any visible quality differences reviewers should accept.

when the reply comes backPush once: ask it to sharpen the weakest part, and to say what it assumed.

How to do it

the tool · the steps · what to avoid

1
Open your PDF file in Adobe Acrobat.
2
Go to the File menu and select Save As Other.
3
Choose Optimized PDF from the submenu.
4
In the PDF Optimizer dialog, click the Settings menu and select Make compatible with: Acrobat 5.0 and later (or newer, if required).
CautionSelecting an older compatibility version may disable Fast Web View.
5
Check the box labeled Optimize for Fast Web View.
NoteThis enables linearization, allowing users to view the first pages of your PDF online before the entire file downloads.
6
Click OK to close the PDF Optimizer dialog.
7
Save the optimized PDF with a new file name to preserve your original document.
Best practiceTest your optimized PDF by opening it in a browser to confirm that the first pages load before the full download completes.

In the appWith the API

Enabling Fast Web View in Acrobat helps your PDF display pages more quickly when viewed online, improving the experience for users with slow connections.

This runs in the Acrobat app - there is no separate API for this task.

Glossary

words on this page

DownsampleTo make an image smaller by removing some of its detail, which reduces the file size.ExampleTo make a large photo fit an email, you might downsample it to reduce its file size.

Unembed fontsTo remove the font information from a PDF, making the file smaller but requiring the font to be on the viewer's computer.ExampleYou unembed fonts from a PDF to reduce its file size before emailing it to a colleague.

DPIDPI means dots per inch, and it tells you how clear an image is when it is scanned.ExampleA scanned photo saved at 300 DPI will usually contain more detail than the same photo at 72 DPI.

The real tasks

the one, listed here

Replace a large hero image with a compressed version so the page loads faster for users on slow connections.

FAQ

about this task

Open your PDF in Acrobat and go to File > Save as Other > Optimized PDF.
In the 'Images' section, set color/grayscale images to about 150 dpi and monochrome to 300 dpi.
Choose 'JPEG quality Medium/High' (around 85%) for images.
In the 'Fonts' section, select 'Subset embedded fonts' and 'Unembed fonts' if not needed.
Remove unnecessary objects and user data under 'Discard Objects' and 'Discard User Data'.

Downsampling means reducing the number of pixels in an image within your PDF. It matters because fewer pixels mean a smaller file size, which helps the PDF load faster. You can control how much quality you lose by choosing the right 'dots per inch' (dpi) setting.

If your PDF is a scanned document, you should use the 'Optimize Scanned Pages' option in Acrobat. This tool is designed to work specifically with scanned content, which often has different characteristics than digitally created PDFs. It can help clean up and compress scanned images more effectively, making the file smaller and clearer.

Color Model	Best Use	File Size Impact
RGB (Red, Green, Blue)	For on-screen viewing (websites, emails)	Generally smaller file size
CMYK (Cyan, Magenta, Yellow, Black)	For professional printing	Generally larger file size

You should unembed fonts to make your PDF file smaller. When fonts are embedded, the font data is stored inside the PDF. If the viewer already has those fonts on their computer, unembedding them removes this extra data, reducing the file size. However, be careful, as unembedding can sometimes change how the document looks if the viewer doesn't have the correct fonts.

Optimize Page Load

When to use it

AI prompts

How to do it

Glossary

The real tasks

Who does this

FAQ

Sources

Adobe help

Other guides

When it fails