Nevermind, I found the solution. I am posting this anyway for case if anyone else has similar problem.

var report = await rs.RenderAsync(new RenderRequest() { Template = new Template() { Recipe = Recipe.ChromePdf, Chrome = new Chrome() { MarginTop = "1cm", MarginBottom = "2cm", MarginLeft = "1cm", MarginRight = "1cm" }, Engine = Engine.Handlebars, Content = templateData, PdfOperations = new List<PdfOperation>() { pdfOperation } }, Data = new { item = item, image = imgBaseSixtyFour } }); using (var fs = File.Create(fileName)) { report.Content.CopyTo(fs); } }