For PDFs, I usually use xournal to add/(re)move pages, add comments, or highlight things, or a command line tool (that uses ghostscript) to format/combine PDFs and gain in size, otherwise inkscape for a more "adobe illustrator" mission (single page only). I have seen and tried many "user friendly" stuff but they never achieved what I was after.
For PDFs, I usually use xournal to add/(re)move pages, add comments, or highlight things, or a command line tool (that uses ghostscript) to format/combine PDFs and gain in size, otherwise inkscape for a more "adobe illustrator" mission (single page only). I have seen and tried many "user friendly" stuff but they never achieved what I was after.