To convert 300dpi JPG file to A4 size PDF file with imageMagick:
convert -density 300 -define pdf:fit-page=A4 source.jpg dest.pdf
Command line options of imageMagick
Scale PDF to A4 with imageMagick
To convert 300dpi JPG file to A4 size PDF file with imageMagick:
convert -density 300 -define pdf:fit-page=A4 source.jpg dest.pdf
Command line options of imageMagick
Scale PDF to A4 with imageMagick