"Oh my God! Using new Mint "modern" theme (Win10 like) the icons inside Inkscape just are screwed up! Horrible and unusable icons! To solve it, just go to Mint Wellcome Screen again and choose Mint "Traditional" theme, and the beautiful and very useful original Inskscape icons will be back."
"This program is greatly usefu! It's command line only, so open a Terminal and type "pdftk --help" or "man pdftk" and you'll have the options explained."