diff --git a/README.md b/README.md
index bfa4a2a..313f7de 100644
--- a/README.md
+++ b/README.md
@@ -131,7 +131,7 @@ The `Section` class can set the following attributes.
 
 - toc: whether to include the headers `<h1>` - `<h6>` of this section in the TOC. Default is True.
 - root: the name of the root directory from which the image file paths starts in markdown. Default ".".
-- paper_size: name of paper size, [as described here](https://pymupdf.readthedocs.io/en/latest/functions.html#paper_size). Default "A4".
+- paper_size: either the name of a paper size, [as described here](https://pymupdf.readthedocs.io/en/latest/functions.html#paper_size), or a list containing the width and height in mm. Default "A4".
 - borders: size of borders. Default (36, 36, -36, -36).
 
 The following document properties are available for assignment (dictionary `MarkdownPdf.meta`) with the default values indicated.
diff --git a/markdown_pdf/__init__.py b/markdown_pdf/__init__.py
index 335bc60..2409886 100644
--- a/markdown_pdf/__init__.py
+++ b/markdown_pdf/__init__.py
@@ -6,7 +6,7 @@
 import fitz
 from markdown_it import MarkdownIt
 from pymupdf import (
-  _as_pdf_document, mupdf, JM_embedded_clean, JM_ensure_identity, JM_new_output_fileptr, ASSERT_PDF,
+  _as_pdf_document, mupdf, JM_embedded_clean, JM_ensure_identity, JM_new_output_fileptr, ASSERT_PDF, Rect,
 )
 
 
@@ -18,7 +18,7 @@ def __init__(
       text: str,
       toc: bool = True,
       root: str = ".",
-      paper_size: str = "A4",
+      paper_size: str|list = "A4",
       borders: typing.Tuple[int, int, int, int] = (36, 36, -36, -36)
     ):
         """Create md section with given properties."""
@@ -81,7 +81,13 @@ def _recorder(elpos):
 
     def add_section(self, section: Section, user_css: typing.Optional[str] = None) -> str:
         """Add markdown section to pdf."""
-        rect = fitz.paper_rect(section.paper_size)
+        if isinstance(section.paper_size, str):
+            rect = fitz.paper_rect(section.paper_size)
+        elif isinstance(section.paper_size, list):
+            # Other paper sizes are in pt, so need to times mm by 2.835.
+            rect = Rect(0.0, 0.0, (section.paper_size[0] * 2.835), (section.paper_size[1] * 2.835))
+        else:
+            raise TypeError("paper_size must be 'str' or 'list'")
         where = rect + section.borders
         html = self.m_d.render(section.text)
         story = fitz.Story(html=html, archive=section.root, user_css=user_css)