flpsed is a WYSIWYG PostScript annotator.
You can't remove or modify existing elements of a document.
But flpsed lets you add arbitrary text lines to existing
PostScript documents (PostScript is a registered trademark of Adobe Systems Incorporated).
Added lines can later be reedited with flpsed.
Using pdftops, which is part of xpdf
one can convert PDF documents to PostScript and also add text to them.
flpsed is useful for filling in forms, adding notes etc.
GsWidget is now part of flpsed.
flpsed is released under the GPL.
fltk-1.3.x based version:
flpsed-0.7.3.tar.gz
sha256 b70bb751bd70af9893ae2369f0789fd79729d0d6d1fee6e0522c4e6f55c7cf6e
flpsed is also available as debian package, FreeBSD port.
A git repository can be found here.