eqn, grap, groff, pic, tbl, troff: add page (#6868)

pages/common/troff.md

@@ -0,0 +1,21 @@
+# troff
+
+> Typesetting processor for the groff (GNU Troff) document fomatting system.
+> See also `groff`.
+> More information: <https://manned.org/troff>.
+
+- Format output for a PostScript printer, saving the output to a file:
+
+`troff {{path/to/input.roff}} | grops > {{path/to/output.ps}}`
+
+- Format output for a PostScript printer using the [me] macro package, saving the output to a file:
+
+`troff -{{me}} {{path/to/input.roff}} | grops > {{path/to/output.ps}}`
+
+- Format output as [a]SCII text using the [man] macro package:
+
+`troff -T {{ascii}} -{{man}} {{path/to/input.roff}} | grotty`
+
+- Format output as a [pdf] file, saving the output to a file:
+
+`troff -T {{pdf}} {{path/to/input.roff}} | gropdf > {{path/to/output.pdf}}`