The following command can change the version of input.pdf to 1.4 and save as output.pdf by using Ghostscript.
gs -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 -dNOPAUSE -dQUIET -dBATCH -sOutputFile=output.pdf input.pdf
The following command can change the version of input.pdf to 1.4 and save as output.pdf by using Ghostscript.
gs -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 -dNOPAUSE -dQUIET -dBATCH -sOutputFile=output.pdf input.pdf