To add Suffix for ** Quotation on Web**, Please follow below mentioned steps.
Step 1: Click on Document Settings, under Quotation.
Step 2: Click on Add Prefixes/Suffixes.
Step 3: Click on Suffixes, slide to right and then click on Quotation.
Now click on +Add Suffix.
Step 4: Add Custom Suffix, and Click on Submit.
Step 5: Click on Update Settings.