# gs > GhostScript is a PDF and PostScript interpreter. > More information: . - To view a file: `gs -dQUIET -dBATCH {{file.pdf}}` - Reduce PDF file size to 150 dpi images for reading on a e-book device: `gs -dNOPAUSE -dQUIET -dBATCH -sDEVICE=pdfwrite -dPDFSETTINGS=/ebook -sOutputFile={{output.pdf}} {{input.pdf}}` - Convert PDF file (pages 1 through 3) to an image with 150 dpi resolution: `gs -dQUIET -dBATCH -dNOPAUSE -sDEVICE=jpeg -r150 -dFirstPage={{1}} -dLastPage={{3}} -sOutputFile={{output_%d.jpg}} {{input.pdf}}` - Extract pages from a PDF file: `gs -dQUIET -dBATCH -dNOPAUSE -sDEVICE=pdfwrite -sOutputFile={{output.pdf}} {{input.pdf}}` - Merge PDF files: `gs -dQUIET -dBATCH -dNOPAUSE -sDEVICE=pdfwrite -sOutputFile={{output.pdf}} {{input1.pdf}} {{input2.pdf}}` - Convert from PostScript file to PDF file: `gs -dQUIET -dBATCH -dNOPAUSE -sDEVICE=pdfwrite -sOutputFile={{output.pdf}} {{input.ps}}`