C'mon. Of course you can do it with B4x but so far nobody did the job for you One way is to display the pdf in a view and get a snapshot (hardcopy) of it. Take a search for snapshot and display pdf or similar.
ok, With this code a i have a img but how can save it in a file?
B4X:
Sub ConvertiPdfImg(nomefile As String)
Dim Render As PDFRenderer
Dim img As Bitmap
Render.Initialize("",Main.pthDOC,nomefile)
For i = 1 To Render.PageCount
img = Render.renderPageforDisplay(i)
' now save img in a file
Next
End Sub