first working POC

main.py

@@ -0,0 +1,27 @@
+#! /usr/bin/env python3
+
+from pypdf import PdfWriter, PdfReader, Transformation
+from pypdf.generic import RectangleObject
+
+with open("input.pdf", "rb") as in_f:
+    reader = PdfReader(in_f)
+    writer = PdfWriter()
+
+    numPages = len(reader.pages)
+    if numPages != 1:
+        exit(1)
+
+    page = reader.pages[0].rotate(90)
+    page = reader.pages[0]
+
+    left = 20
+    bottom = 450
+    right = 570
+    # calculate last value to get a 3:2 rectangle
+    top = bottom+((right-left)/3)*2
+
+    page.mediabox = RectangleObject((left, bottom,right,top))
+    writer.add_page(page)
+
+    with open("out.pdf", "wb") as fh:
+        writer.write(fh)