That's why page dimensions are things like "/CropBox [0.0 0.0 595.27576 841.89001]". PDF points are the same as Postscript points, 1/72 of an inch, that is 25.4/72 mm. So those numbers mean a page 210mm wide and 297mm high: A4.
Yes, the actual values are points, and one point is 1/72 of an inch, which is the same, as if the values were in inches. I just wanted to point out, that the units are physical (unlike "logical" units in an SVG or in a webpage).
That's why page dimensions are things like "/CropBox [0.0 0.0 595.27576 841.89001]". PDF points are the same as Postscript points, 1/72 of an inch, that is 25.4/72 mm. So those numbers mean a page 210mm wide and 297mm high: A4.