dpi in pdf

[Giulia225177485jl0]

How can I check and possibly change the dpi of images in a pdf file using Adobe Acrobat Pro? I'm using Windows 11

[Document Geek · Accepted solution]

Do you want to increase or decrease the resolution? If decrease, you can optimize the PDF.

If increase, there is no way to do that in Acrobat.

To check the resolution, use Preflight.

[Document Geek · Accepted solution]

Do you want to increase or decrease the resolution? If decrease, you can optimize the PDF.

If increase, there is no way to do that in Acrobat.

To check the resolution, use Preflight.

[Luke Jennings3 · Accepted solution]

Another option is to go to Tools> Print Production> Output Preview, change the Preview: to Object Inspector, click on an object. You can open the image in Photoshop (Tools> Edit pdf> Edit using:> Photoshop) where you can  change the dpi, or optimize the pdf to downsample all images, File> Save as other> Optimized pdf.

[Giulia225177485jl0]

I want to check that the images are not more than 300 dpi, they can be even less. Can you explain to me how I can check and decrease the dpi? The images are a lot because is a portfolio of 100 pages. Thank you!

[Giulia225177485jl0]

I want to check that the images are not more than 300 dpi, they can be even less. Can you explain to me how I can check and decrease the dpi? The images are a lot because is a portfolio of 100 pages. Thank you!

[Dave Creamer of IDEAS]

As @Document Geek suggested, use PDF Optimizer

[Dave Creamer of IDEAS]

This is what I call a "desperation mode" process:

Right click on the image. (It should open in Photoshop; if not, check your Acrobat preferences.)

In PS, turn on resample and adjust the resolution. 

Save--it will update in the PDF.

Repeat as necessary.

If you add too much resolution this way, you will soften the image. You can try running some Smart Sharpen, but nothing will make it as good as having enough resolution to begin with. However, I look it as better to have a slightly soft image than a pixelated image. 

I've attached a PDF comparing a high-res, a pixelated, and an up-sampled image.