Use this regex:
(?<=Description\s*:\s*)([\S\s]*?)(?=\b(Article|Sold Date)\b)
This will work for both the scenarios.
System.Text.RegularExpressions.Regex.Match(strPDFData,"(?<=Description\s*:\s*)([\S\s]*?)(?=\b(Article|Sold Date)\b)").Value.Trim
Output:

