string AllPDF = "";
int CountPDF = 0;
AllPDF = txtInput.Text;
string[] AllPDF2 = AllPDF.Split(';');
List<string> PDF = new List<string>();
PDF.AddRange(AllPDF2);
while (PDF.Count != CountPDF)
{
    File.Delete(AllPDF2[0 + CountPDF] + ".pdf");
	CountPDF++;
}