UPDATE #1: first of all thanks for all your nice comments!! just a tip that may work for you guys, after googleing, I found a superb trick to shrink the size of PDFs, I reduced with it one PDF of 300 MB to just 15 MB with an acceptable resolution! and all of this with the good ghostscript, here it is: gs -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 -dPDFSETTINGS=/default -dNOPAUSE -dQUIET -dBATCH -dDetectDuplicateImages -dCompressFonts=true -r150 -sOutputFile=output.pdf input.pdf

In this way you wouldn't need to install anything else, just work with what you already have installed in your system (at least both come by default in my box). In both cases the ouput resolution is much higher and better than this way using convert: convert -density 300x300 -quality 100 mine1.pdf mine2.pdf merged.pdf

Or even this way for an improved version for low resolution PDFs (thanks to Adriano for pointing this out): gs -dBATCH -dNOPAUSE -q -sDEVICE=pdfwrite -dPDFSETTINGS=/prepress -sOutputFile=merged.pdf mine1.pdf mine2.pdf Try the good ghostscript: gs -dBATCH -dNOPAUSE -q -sDEVICE=pdfwrite -sOutputFile=merged.pdf mine1.pdf mine2.pdf

Pdf combine online free