A great first effort! Many thanks!
After some use I do have these suggestions:

1. When User changes LayoutMode the ZoomLevel property changed event should also be fired. I have a Numeric Textbox to adjust viewer ZoomLevel and would like to see its text update on a LayoutMode change. However when LayoutModeChanged fires the ZoomLevel has not yet changed nor does ZoomLevelChanged later fire.
2. The toolbar item for Fit to Width should be a Toggle in all cases, i.e. toggling between Fit Width and Fit Height (or Fit Page) and should be effective at all times (sometimes has no effect if LayoutMode changed to Single Page).
3. The toolbar item to toggle LayoutMode should honor an assignment of its text property.
4. I'm currently using the change in VisiblePagesCount to determine the document is visible. However a "Loaded" event might be even better.
5. I would like to release the viewer's memory of the document before closing the XAML page. An Unload command would be helpful. For now I just assign Source = null.

Support for FileDocumentSource

Ref# 1106424. We are using Kendo Scheduler in our Web application to show the recurring appointments. Similarly, We need the Recurring appointments to the RadCalendar for Xamarin.Forms in Mobile to aligned with Android and IOS.   

Add support for header and footer that scroll with the content of the list view.

StrokeColor and Labels colors are not properly mapped in native Chart.

When the language of the iOS devices is changed to "Right to Left" the SuggestionView is not shown correctly. 

Two of the bar series used CombineMode="Stack" and one - CombineMode="Cluster". The BarSeries with CombineMode="Cluster" overlaps the series with CombineMode="Stack".

Request for polar axis series types:

- Radar Series
- Phasor
- Polar

In Xamarin.Forms, there is no multiline text box editor in RadDataForm.

The scenario in which the issue is reproducible is when one of the tabs of a RadTabView contains a RadSideDrawer. Switching the view a couple of times causes an exception to be thrown when trying to open the tab that contains the RadSideDrawer. 

The issue is reproducible in UWP and Android.

Available in minor release 2018.1.0315. It will also be available in the R2 2018 release.

When setting HorizontalItemSpacing or VerticalItemSpacing to the layout, the item spacing appears to be applied twice to the item. 
When setting BackgroundColor to the ItemStyle the background leaks beyond the boundaries of the item.

The issue can be observed in the AutoCompleteView control.

By default, the RadCalendar in DayView mode starts at midnight which is not very intuitive for all scenarios. The native controls expose APIs to control the starting time so we can consider exposing StartTime/EndTime properties for the users to control.

ArgumentOutOfRangeException is thrown when two buttons are pressed at a time

When the Mask property is set to letters and digits, the Mask accepts symbols too.

When in MonthView, you're navigating to WeekView on CellTap event, and DisplayDate and SelectedDate are bound to the same value, DisplayDate is not updated on iOS (works properly on Android)

Introduce Android Snackbar for Xamarin.Forms that needs to work on app level