How can I create a shortcut to open a selected file with a particular Application?

I am trying to find a way to create a shortcut for opening a pdf file with a particular application. This is what i do currently(manually):

Step 1. I have a pdf file say MyBook.pdf. I right click on this pdf so that a popup window appears with many options like:

Cut

Paste

Copy

Open with other application

Move to trash

Step 2. I chose/click Open with other application from the above menu and a new popup menu opens up with different options like:

Document Viewer

Google Chrome

Text Editor

Sublime Text

Okular

Step 3. I chose Okular from the above menu and the pdf opens up using Okular.

What i want is that these 3 manual steps should be encapsulated in keyboard shortcut like Ctrl + O + P

Is this possible in Ubuntu 18.04 ?

PS: I am using nautilus-folder-handler.desktop on Ubuntu 18.04

Summary

I want to be able to select any arbitrary pdf by single left click and then press a custom shortcut key that will open that selected pdf using a particular application such as okular.

I noticed that there is options like Ctrl+C for copying Ctrl+X for moving, Ctrl+I for checking the properties of a file just by a single left click and then pressing the corresponding shortcut. I want to do exactly this. That is the user left clicks one time on a file and then press the shortcut which will open the file with a given application.

1. A shortcut

You can use a selected file as argument to run a script (from this answer):

Setup

• run sudo apt install python3-pyperclip xdotool to install dependencies.
• Copy the script below into an empty file, save it as open_with_okular, and make it executable.

#!/usr/bin/env python3
import subprocess
import pyperclip
import time

time.sleep(1)
subprocess.call(["xdotool", "key", "Control_L+c"])
subject = pyperclip.paste()
subprocess.Popen(["okular", subject])

• Create a shortcut to run the script. It will copy the (path + name of) the file, feed it to the script as argument.

2. Using nautilus scripts

Not literally what you are asking, but the easiest and cleanest is to use a nautilus script.

Since you are using nautilus, you can add a custom action:

• Create (if necessary) the directory ~/.local/share/nautilus/scripts

• Create a tiny script in the directory:

  #!/bin/bash
  okular "$1"
  

  call it open with okular or something, and make it executable.

Now opening the file is directly possible from rightclick -> Open with Okular.
The file will be passed as the argument to the script.

Settings>Devices>Keyboard
Then locate custom shortcuts and set your desired shortcut ....
The command field should be

okular <path-to-your-pdf>/name-of-file.pdf

For example, if your pdf file is "notes.pdf" in Downloads, then the command would be

okular ~/Downloads/notes.pdf  

Hope it helps !

P.S.: Don't hesitate to ask any doubts if necessary