Problem:

You need to know the resolution and color space for images incrustated (inside) in a pdf file.

Solution:

To solve it, you can use command pdfimages in the Terminal.

Step by step:

  1. Open the Terminal, type Ctrl+Alt+T
  2. Type the command, specify the pdf filename. 
    pdfimages -list myfile.pdf

    you’ll get a list with the images and their properties, like this:

    pdfimages -list myfile.pdf

    you’ll get this output table:

    page   num  type   width height color comp bpc  enc interp  object ID x-ppi y-ppi size ratio
--------------------------------------------------------------------------------------------
1      0 image     240   240  rgb     3   8  image  no       233  0   180   180 8088B 4.7%
13     4 image     209   177  rgb     3   8  jpeg   no       415  0   219   219 6412B 5.8%

Plus 01!

Get the color space from a pdf file

identify -verbose myfile.pdf

Plus 02

Get the color space from a image file (jpg or png)

identify -verbose myimage.jpg | grep Colorspace

Source:

https://unix.stackexchange.com/questions/316760/what-are-gnu-linux-tools-for-checking-pdf-documents-before-publishing
https://stackoverflow.com/questions/6241282/converting-pdf-to-cmyk-with-identify-recognizing-cmyk