You can create Custom List Item Menu using SharePoint Designer.
Open the Site using the SharePoint Designer->Select the list where you would like to create the list action menu->Custom Action Button -> “List Item Menu” to create the custom list action item:
Per my test in my sharepoint 2016 environment, I install Adobe Acrobat Reader DC, then I can open the pdf file in IE.
But if you want to edit the PDF file, you should buy the service.
And there are some other PDF products in the article below.
Adobe Acrobat Alternative.