At the moment DAZ Studio doesn't let you choose the resolution in pixels per inch of your image - if you need a high resolution image for print you will have to work out how big it needs to be in pixels, width in inches x desired resolution in pixels per inch = width in pixels height in inches x desired resolution in pixels per inch = height in pixels and render at that size and then change the resolution in PPI without changing the file size in your image editor - for example, in Photoshop make sure Resample image is unchecked. This doesn't hurt the quality of the image - it just tells the printer how big to make each pixel of the image.
Typical Internet Resolution for graphics is 72 dpi. For printed material, pictures and graphics are usually 300 dpi, but sometimes as high as 600 dpi. If you wish to have a render that will print out at 10 inches x 8 inches at 300 dpi, you need to multiply 300 by the inches. So, in this case, 10 inches x 8 inches would be 3,000 pixels by 2,400 pixels. This is the size you would need to render in DAZ Studio to have a picture that could be printed out at 10" x 8" at 300 dpi.
To change the resolution (pixel dimensions) in DAZ Studio, go to RENDER --> Render Settings. In the box labeled 'Dimensions,' change the 'Presets' drop-down to 'Custom.' Then you can type the pixel dimensions into the two white boxes just below. You may need to render to 'New Window' or 'Image File.' These options are in the 'Render to' box just a little further down. Click 'Accept' to keep the changes without doing a render right away. Click 'Render' to keep the settings and immediately begin the render process.