Chapter 4 - killall & pkill

"-signal" is an option so the order is irrelevant. It is just showing special attention to the -signal option. Just try it (before posting). The following lines all do the same thing:
pkill -44 -u 1000 cat
pklll cat -u 1000 -44
pkill -u 1000 cat -44

etc, order is irrelvant, even where the pattern goes

Hi,

You always can do 'man ' to see the available information of the associated man pages about the command. In this case 'man pkill' shows the following:

PGREP(1) User Commands PGREP(1)

NAME
pgrep, pkill - look up or signal processes based on name and other attributes

SYNOPSIS
pgrep [options] pattern
pkill [options] pattern

DESCRIPTION
pgrep looks through the currently running processes and lists the process IDs which match the selection criteria to stdout. All the criteria have to match. For example,

[...]

OPTIONS
-signal
--signal signal
Defines the signal to send to each matched process. Either the numeric or the symbolic signal name can be used. (pkill only.)

[...]

Regards,
Luis.