How do I pin a file shortcut to Ubuntu dock?

Follow the steps below.

1. Create a .desktop file (say spreadsheet1.desktop) in ~/.local/share/applications/ directory. You can do that by running the following command in Terminal:

   touch ~/.local/share/applications/spreadsheet1.desktop
   

2. Open the file with a text editor, for example by running

   gedit ~/.local/share/applications/spreadsheet1.desktop
   

   Then add the following lines:

   [Desktop Entry]
   Name=XYZ spreadsheet
   Exec=xdg-open /full/path/to/XYZ-spreadsheet.ods
   Comment=Launch XYZ spreadsheet
   Terminal=false
   Type=Application
   Icon=x-office-spreadsheet
   

3. Save the file.

4. Click on "Activities" or "Show Applications" and search for "XYZ spreadsheet". It should appear.

5. Right click on it and mark as favourite.

Note: The xdg-open command opens the file with the default application associated with the file-type. You can alternatively set

Exec=libreoffice /full/path/to/XYZ-spreadsheet.ods

in the .desktop file to always open the file with LibreOffice Calc.