Open-source graphical front-end for Ghostscript on Windows/Linux/macOS, giving Ghostscript's command-line PostScript/PDF interpreter a proper windowed UI: views and navigates PostScript and PDF files, and converts sequences of PDF pages to image files (from raw bitmap through TIFF-pack formats) at a selectable output resolution. Originally developed by Russell Lang alongside Ghostscript itself.
Its SourceForge project page (the previous source link) now 404s — the project has no clear current official home; linked to its CTAN listing instead as the most stable remaining reference.