The main point is that i can not ensure that the user created the files in order. In some cases the file 3 could have been created before file 2, for example.
it has this output as the FullfilePaths are Lexically sorted
In your case we would recommend to setup a more specific sorting using the filename without extension and using some parts from the filename for a numerical sorting.
(From x In Directory.GetFiles("YourPath", "*.pdf")
Let fname = Path.GetFileNameWithoutExtension(x)
Let shlp = New String(fname.Where(Function(s) Char.IsDigit(s) OrElse s.Equals("."c)).ToArray)
Let arrSplit = shlp.Split("."c)
Let arrSort = If(arrSplit.Length = 2, arrSplit, {shlp,"-1"})
Order By CInt(arrSort(0)), CInt(arrSort(1))
Select f=x).toArray
“306842-4.1”
keep only digits and dots → “3068424.1”
Split on dot into two parts {“3068424”,“1”}
Order it first on CInt(“3068424”), second on CInt(“1”)
do some defensive handlings when no dot is present