Add description to SavePDFGui

This commit adds a decstrings of the SavePDFGui.

re: #27774

Framework/DataHandling/inc/MantidDataHandling/SavePDFGui.h

@@ -13,7 +13,14 @@
 namespace Mantid {
 namespace DataHandling {
 
-/** SavePDFGui : TODO: DESCRIPTION
+/** SavePDFGui : Saves a workspace containing a pair distrebution function in 
+a format readable by the PDFgui package.
+
+Required Properties:
+<UL>
+<LI> InputWorkspace - An input workspace with units of Atomic Distance </LI>
+<LI> Filename - The filename to use for the saved data </LI>
+</UL>
  */
 class DLLExport SavePDFGui : public API::Algorithm {
 public:

Framework/DataHandling/src/SavePDFGui.cpp

@@ -43,7 +43,7 @@ const std::string SavePDFGui::summary() const {
 void SavePDFGui::init() {
   declareProperty(std::make_unique<WorkspaceProperty<>>("InputWorkspace", "",
                                                         Direction::Input),
-                  "An input workspace.");
+                  "An input workspace with units of Atomic Distance.");
   declareProperty(std::make_unique<API::FileProperty>(
                       "Filename", "", API::FileProperty::Save, ".gr"),
                   "The filename to use for the saved data");