Reducing the Sizes of Big Files

[Vlad23546300ov6c]

I have many files whose sizes are big because of high-quality scans of books. Some of them were downloaded from archive.org, which contains a lot of scanned books. Does anyone know what function in Adobe Acrobat can be used to significantly reduce the size of big files?

I have tried going to Files > Save as Other > Reduced Size PDF, but the size was not reduced significantly. I have a file which is over 100mb and want to reduce its size to about 5mb.

[Test Screen Name]

Save as Optimized PDF gives you more controls. Experiment with compression and resolution. But ultimately scanned books are big things. If there was a simple treatment to "fix" this while keeping quality, archive.org would have done it already.

[Vlad23546300ov6c]

I tried using the option Optimized PDF many times with different parameters but was not able to attain the desired size without blurring the scans.

Some scanned books on archive.org have small sizes, and yet their quality is good, whereas others have very big sizes, and I still do not know how to reduce them without making texts in the scans unreadable.