Install MariaDB on Ubuntu 18.04 LTS

Visit the following link and choose the desired version of MariaDB,

https://downloads.mariadb.org/

Following commands will add repository and install MariaDB 10.3,

sudo apt-get install software-properties-common

sudo apt-key adv --recv-keys --keyserver hkp://keyserver.ubuntu.com:80 0xF1656F24C74CD1D8

sudo add-apt-repository 'deb [arch=amd64,arm64,ppc64el] http://mirrors.tuna.tsinghua.edu.cn/mariadb/repo/10.3/ubuntu bionic main'

sudo apt update

sudo apt install mariadb-server

Add metadata to PDF files

Master PDF Editor is a PDF editor application and can act as metadata editor. The user can add metadata to an existing PDF files (book, articles etc.) Metadata can give more document visibility while others searching in World Wide Web.

Installation of Master PDF Editor
Download the application
Download the DEB file from following link.
https://code-industry.net/free-pdf-editor/#get

Installation of DEB package
Apply the following command to install the package,

dpkg -i master-pdf-editor*

The application will open from Applications > Office > Master PDF Editor

Adding metadata to PDF file
Open the PDF file with Master PDF Editor

Editing mode of a PDF file.

Open File > Properties to add the metadata.

Save and close the document after adding the metadata.

Right click on the PDF file from file manager and select properties. Newly added metadata visible.