Having pigs in the forest - to be hiding something.
The tax man would go from farm to farm back in the old days and count the number of pigs. The farmers would be taxed accordingly. Naturally, when you heard the tax man was coming, you'd send some pigs into the forest so that you'd be taxed less. Norwegian. :)
In addition to what's already mentioned in the comments, shout out to Inkscape. I guess it's similar to LibreOffice Draw, but I prefer the user experience of Inkscape. Probably more for single-page PDFs.