Updated help message.

pdfmarks

@@ -9,12 +9,13 @@ show_help() {
 	printf "	-s=SEP\tseparate arguments of COMMAND using the characters of SEP instead of space\n"
 	printf "\n"
 	printf "Renumbers the pages of FILE according to COMMAND, where COMMAND is of the format:\n"
-	printf "	[ <physical_page> <logical_page> [<page_style>] [<page_label>] ]*\n"
+	printf "	[ <physical_page> <logical_page> [<page_style>] [<page_label>] [<physical_page_end:logical_page_step>] ]*\n"
 	printf "where\n"
 	printf "	<physical_page> is a physical page number;\n"
 	printf "	<logical_page> is a logical page number;\n"
-	printf "	<page_style> [optional] is one of 'D' (decimal Arabic), 'R' (upper-case Roman), 'r' (lower-case Roman), 'A' (upper-case letters), 'a' (lower-case letters), or '-' for unspecified;\n"
-	printf "	<page_label> [optional] is a label for prefixing page numbers.\n"
+	printf "	[<page_style>] is one of 'D' (decimal Arabic), 'R' (upper-case Roman), 'r' (lower-case Roman), 'A' (upper-case letters), 'a' (lower-case letters), or '-' for unspecified;\n"
+	printf "	[<page_label>] is a label for prefixing page numbers.\n"
+	printf "	[<physical_page_end:logical_page_step>] steps logical page numbers by <logical_page_step> from physical page <physical_page> until <physical_page_end> (instead of by one).\n"
 	printf "Arguments in COMMAND may alternatively be delimited by the '#' charater, rather than by spaces (the ' ' character).\n"
 	printf "If the COMMAND argument is not specified, then it is read as a single line from standard input.\n"
 }