I’m not able to view the custom field I created in transaction PDFs. What should I do to display it?

You have to enable the Show in All PDFs to display the custom field in a transaction’s PDF. Here’s how:

Go to Settings and select Preferences.
Go to the module in which you created the custom field (say Invoices).
Go to the Field Customisation tab.
Hover over the custom field which you want to be display in the transaction’s PDF and click Edit.
On the Edit Custom Field page, choose Yes next to Show in All PDFs.
Click Save.