ListDensityPlot generates a huge pdf output

Question

I have been using ListContoutPlot to plot some data and then export it to a pdf file.

Seeing as the ListContourPlot has its own ideas regarding the placement of contours I've switched to ListDensityPlot, thus having the right contours (as I wanted).

But this resulted in a new issue for me, before the switch the outputted pdf file's size was ~5MB, now I'm getting file's size at around ~200MB. What options do I have if I want to maintain at least one high-quality output file (vector based image)?

I'm trying to keep an un-rasterized image file, but not at all cost.

EDIT
Minimal working example:

On Mathematica 10.0.1.0, the resulting pdf's file size are 74.2kB for the ListContourPlot and 22.6MB for the ListDensityPlot.

data=Table[{x,y,RandomInteger[{1,7}]},{x,Range[100]},{y,Range[100]}];
op={ColorFunctionScaling->True,ColorFunction->"DarkBands",InterpolationOrder->0};
con=ListContourPlot[data,Evaluate@op];
den=ListDensityPlot[data,Evaluate@op];
Export["./con.pdf",con,"PDF"]; (* 74.2kB *)
Export["./den.pdf",den,"PDF"]; (* 22.6MB *)

Answer 1

Try this:

Export["den.pdf", den, "PDF", ImageResolution -> 600, "AllowRasterization" -> True];

(* 82Kb *)

However, please, be advised that `AllowRasterization" needs avdavanced versions of PDF as documentation note.

I have no problem with Acrobat Reader DC in Windows 7 and MMA 11.2