I hava a specific string that I want to replace 

```
string gerneralRootPath = docTab.Rows[0]["URL"].ToString();
string documentName = docTab.Rows[0]["NAME"].ToString();

var connectNamesAndURL = new StringBuilder(gerneralRootPath);
connectNamesAndURL.Remove(30,20);
connectNamesAndURL.Insert(30, documentName);
gerneralRootPath = connectNamesAndURL.ToString();

```

The output of gerneralRootPath is 
**"Documents/Z\_Documentation/PDF/sales.2010+Implementation+Revised+Feb10.pdf"**

The output of is documentName is 
**"doc123"**

My gole is to remove everything after /PDF/.. so that final string looks like this 
**Documents/Z\_Documentation/PDF/doc123**

So how can I remove everything after the /PDF/..