請參考 https://www.adobe.com/devnet-docs/acrobatetk/tools/AdminGuide/pdfviewer.html
裡面的 Solution 2: GPO policy,
我是透過類以方法,來設定預設開啟用IE,預設MAIL用OUTLOOK,預設Adobe Reader.

具體作法:
1.做一個XML,丟到每個USER電腦中.
2.透過GPO設定關聯檔參考到步驟 1 的XML
3.套用後,USER下次登入即生效.
4.請先測試後,再套用到所有USER.

以下是自用的XML,請依需求自行修改

<?xml version="1.0" encoding="UTF-8"?>
<DefaultAssociations>
	<Association Identifier=".pdf" ProgID="AcroExch.Document.DC" ApplicationName="Adobe Acrobat Reader DC" />
	<Association Identifier=".pdfxml" ProgID="AcroExch.pdfxml" ApplicationName="Adobe Acrobat Reader DC" />
	<Association Identifier=".acrobatsecuritysettings" ProgID="AcroExch.acrobatsecuritysettings" ApplicationName="Adobe Acrobat Reader DC" />
	<Association Identifier=".fdf" ProgID="AcroExch.FDFDoc" ApplicationName="Adobe Acrobat Reader DC" />
	<Association Identifier=".xfdf" ProgID="AcroExch.XFDFDoc" ApplicationName="Adobe Acrobat Reader DC" />
	<Association Identifier=".xdp" ProgID="AcroExch.XDPDoc" ApplicationName="Adobe Acrobat Reader DC" />
	<Association Identifier=".pdx" ProgID="PDXFileType" ApplicationName="Adobe Acrobat Reader DC" />
	<Association Identifier=".api" ProgID="AcroExch.Plugin" ApplicationName="Adobe Acrobat Reader DC" />
	<Association Identifier=".secstore" ProgID="AcroExch.SecStore" ApplicationName="Adobe Acrobat Reader DC" />
	 <Association Identifier=".website" ProgId="IE.AssocFile.WEBSITE" ApplicationName="Internet Explorer" />
	  <Association Identifier="http" ProgId="IE.HTTP" ApplicationName="Internet Explorer" />
  <Association Identifier="https" ProgId="IE.HTTPS" ApplicationName="Internet Explorer" />
   <Association Identifier=".htm" ProgId="htmlfile" ApplicationName="Internet Explorer" />
  <Association Identifier=".html" ProgId="htmlfile" ApplicationName="Internet Explorer" />
  <Association Identifier="mailto" ProgId="Outlook.URL.mailto.15" ApplicationName="Outlook 2016" />
</DefaultAssociations>