Add Pages to PDFs in UWP

New pages can be added to a new document from one or more document sources via an Editor.Job:

// Create a job from a source document.
var job = new PSPDFKit.Document.Editor.Job(_documentOne);

// Create a new page from a second document at page index 2.
var newPage = NewPage.FromPage(_documentTwo, 2);

// Append the new page to your job's document at page index 5.
await job.AddPageAtIndexAsync(newPage, 5);

// Create a new PDF and get its `StorageFile`.
var newDocument = await Editor.NewStorageFileFromJobAsync(job);