AutoCAD .NET :: Batching Export To PDF

I've got an exiting problem while trying to batch pdf export.

My task is quite simple: first, look through the drawing (all the lists and model space) and find all dynamic blocks with effective name "SheetGOST", case it's a drawing frame; second, export areas surrounded by those frames to pdf page by page. I've decided that plotting areas via "DWG To PDF.pc3" would be the easiest way.

Practically all the steps made: I get collection of blocks, I know howto print one of them to pdf, and it,s working correctly. The problem is, when I try to plot all the areas in cycle, in output pdf I get num of pages according to num of lists, and only the last area from the list. Test document contains 24 blocks on 3 lists, I get 3 page pdf with 7th, 22th and 24th frame printed.

The code is:
 
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[CommandMethod("PlotToPdf")] static public void MultiSheetPlot() { Document doc = Application.DocumentManager.MdiActiveDocument; Editor ed = doc.Editor; Database db = doc.Database; Transaction tr = db.TransactionManager.StartTransaction(); using (tr) { List<GostBlk> BlocksToPlot = new List<GostBlk>(); List<Layout> LayList = new List<Layout>(); GetGostStampCollection(db, ed, tr, ref BlocksToPlot, ref [code]........