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 'downsampling' in PDF optimization and why does it matter?

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 my PDF is a scanned document, how should I optimize it?

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.

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

Why should I unembed fonts when optimizing a PDF?

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 scanned PDF for OCR and searchability in Adobe Acrobat — How-to & AI prompts

AI prompts

3 ways to ask · copy any one

AExecute — “help me do it”Please optimize my scanned PDF for OCR and searchability...…+

Please optimize my scanned PDF for OCR and searchability using Adobe Acrobat. The file is [insert file location].

when the reply comes backWould you like tips on checking if your PDF is searchable?

BImprove — “do it better”Can you enhance the OCR quality on my scanned PDF...…+

Can you enhance the OCR quality on my scanned PDF in Adobe Acrobat so the text is more accurate? The file is [insert file location].

when the reply comes backNeed help with saving or sharing your optimized PDF?

CDecide — “help me choose”What OCR settings should I use for my scanned PDF...…+

What OCR settings should I use in Adobe Acrobat to get the best results for my scanned PDF? The file has [describe file, e.g., handwritten/printed, language].

when the reply comes backWant to know how to fix poor OCR results?

How to do it

the tool · the steps · what to avoid

1
Open the scanned PDF file in Adobe Acrobat.
2
Select File > Save as Other > Optimized PDF.
3
In the PDF Optimizer dialog, select Scanned Pages from the left panel.
4
Adjust the image compression and resolution settings to balance file size and quality as needed.
Best practiceLowering image resolution too much can reduce OCR accuracy; test settings with a sample page before applying to the full document.
5
Check the box for Make Searchable (Apply OCR).
6
Choose the correct document language for OCR from the available options.
CautionSelecting the wrong language may result in poor text recognition.
7
Click OK to apply optimization and OCR.
8
Save the optimized, searchable PDF with a new file name.

In the appWith the API

Preview the optimized PDF to ensure both text searchability and image quality meet your needs before distributing the file.

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

Glossary

words on this page

Scanned PDFA PDF made from pictures of pages, not real text.ExampleThe old book you downloaded was a 'Scanned PDF', so you couldn't highlight any text directly.

OCROCR stands for Optical Character Recognition. It is technology that turns images of text into real text you can search and copy.ExampleAfter scanning a paper invoice, OCR allows you to copy the vendor's name from the image.

SearchableSearchable means you can find words by using the search tool.ExampleBecause the document is searchable, you can easily find the specific paragraph you need.

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

In Adobe Acrobat, you can use the 'Scan & OCR' tool to recognize text in your scanned PDF. This turns the picture-based pages into real text you can search, copy, or highlight.

OCR stands for Optical Character Recognition. It means the computer looks at the image of your document and changes the letters and numbers into real text you can work with.

If your PDF was made by scanning, it is just pictures of pages. You need to run OCR in Adobe Acrobat to turn those pictures into searchable text.

A searchable PDF lets you find words, copy text, and highlight sentences. A regular scanned PDF is just an image, so you can’t search or select text until you use OCR.

You should optimize a scanned PDF for OCR anytime you want to search for words, copy text, or make the document easier to read and use on a computer.

Optimize scanned PDF for OCR and searchability

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