Yeah, I don't know. I know that there are softwares specific for invoicing but I've never used one, nor did I use to send too many invoices. Most of the time I was an employee, doing some other freelances, so it wasn't too much to keep track.

I used Inkscape because I was more used to it, working with graphics most of my life. LibreOffice is probably easier. But I don't know how that's supposed to be done with proprietary softwares either.

Hopefully someone with more experience on this can help him.