tlmgrでパッケージを探し、導入する

実際のところ

# tlmgr update --self --all

# tlmgr search --global watermark

tlmgr: package repository https://ftp.kddilabs.jp/CTAN/systems/texlive/tlnet (verified)
draftcopy - Identify draft copies
draftwatermark - Put a grey textual watermark on document pages
dviasm - A utility for editing DVI files
...

# tlmgr install draftwatermark

# tlmgr info --only-installed draftwatermark
package:     draftwatermark
category:    Package
shortdesc:   Put a grey textual watermark on document pages
longdesc:    The package provides a means to add a watermark (typically a light gray piece of text) on every page or on the first page of a document. Typical usage may consist in writing words such as DRAFT or CONFIDENTIAL across document pages. The package performs a similar function to that of draftcopy, but its implementation is output device independent. As of today, the package relies on the new shipout hooks directly provided by LaTeX. For users of older versions of LaTeX, the package also provides a legacy version of itself (that is automatically loaded, currently being at release 2.3) which relies on the everypage package. Note that this legacy version will progressively lag behind in terms of features.installed:   Yes
revision:    57099
sizes:       run: 17k
relocatable: No
cat-version: 3.0
cat-license: lppl1.3
cat-topics:  editorial watermark
cat-related: eso-pic
cat-contact-bugs: https://github.com/callegar/LaTeX-draftwatermark/issues
cat-contact-repository: https://github.com/callegar/LaTeX-draftwatermark
cat-contact-home: https://github.com/callegar/LaTeX-draftwatermark

必要なパスには入ったのでtexのベースファイルに

\usepackage[ firstpageonly=false , scale=0.5, color={[gray]{0.9}}, text=YOURMSG ]{draftwatermark}