需引用Acrobat库.  
Dim app    As Acrobat.AcroApp
    Dim avdoc  As Acrobat.AcroAVDoc
    Dim i      As Byte
    Set app = CreateObject("AcroExch.App")
    Set avdoc = CreateObject("AcroExch.AVDoc")
    app.Show
    avdoc.Open "c:\sm.pdf", "sm" '第二个参数为另存为对话框的默认文件名
    app.MenuItemExecute ("SaveAs")
    app.Hide
    app.Exit
    Set app = Nothing