Minor fixes to the webpdf exporter (#1419)

docs/source/customizing.rst

@@ -100,8 +100,6 @@ although any other resource from the base template can be overriden in the deriv
 For example, inspecting the content of the ``classic`` template located in
 ``share/jupyter/nbconvert/templates/classic``, we find the following content:
 
-Inspecting the content of the ``classic`` template we find the following file structure:
-
 .. code::
 
     share/jupyter/nbconvert/templates/classic

nbconvert/exporters/webpdf.py

@@ -42,22 +42,23 @@ async def main():
             await page.goto('data:text/html,'+html, waitUntil='networkidle0')
             await page.waitFor(100)
 
+            # Floating point precision errors cause the printed
+            # PDF from spilling over a new page by a pixel fraction.
             dimensions = await page.evaluate(
               """() => {
                 const rect = document.body.getBoundingClientRect();
                 return {
-                  width: rect.width,
-                  height: rect.height,
+                  width: Math.ceil(rect.width) + 1,
+                  height: Math.ceil(rect.height) + 1,
                 }
               }"""
             )
             width = dimensions['width']
             height = dimensions['height']
-
+            # 200 inches is the maximum size for Adobe Acrobat Reader.
             pdf_data = await page.pdf(
               {
-                'width': width,
-                # 200 inches is the maximum height for Adobe Acrobat Reader.
+                'width': min(width, 200 * 72),
                 'height': min(height, 200 * 72),
                 'printBackground': True,
               }