@joojaa, in InDesign, if you have an untagged RGB image in a document and convert to CMYK when you export a PDF, InDesign have to guess the RGB profile. And in that case it assumes the RGB image to have the profile chosen as Document RGB. When I mention Working Space I'm talking about how the placed image looks when editing it in Photoshop. If
Open Photoshop, change all the PNG files to PSD in CMYK mode, replace them in the InDesign document. PNG doesn't support CMYK. Home printers are designed to print RGB files, most can't print CMYK images. The same is not true for commercial print services, especially where spearations may be needed. In this case, the RIP will use the spot color if available or if not, it will convert Pantone's more precise LAB color values specified as the “alternate color space” to the press' CMYK color space. If you know that the press definitely won't have the spot colors, set the Ink Manager as follows: Select the object or objects you want to change. Click the Fill or Stroke box in the Swatches panel or the Toolbox. (If the Gradient Fill box is not visible, choose Show Options in the Gradient panel menu.) To open the Gradient panel, choose Window > Color > Gradient, or double-click the Gradient tool in the Toolbox.