Page size won't change even after using geometry package

Question

I'm trying to change the page size of my thesis document. As adviced in other threads, the graphics package can be used for this purpose. I currently have the following command where I also specified the page margins.

\usepackage[pass,paperheight=26cm,paperwidth=19cm,top=20mm,bottom = 15mm, left = 30mm, right = 30mm ]{geometry} 

On the thesis document, the pdf page size wont change from 8.50x11inch. The thesis document contains inputs from 4 other files (4 chapters) too. If I create a new tex file and have the same command, the pdf document will have the correct dimensions. For instance,

\documentclass[11pt]{report}
\usepackage[paperheight=26cm,paperwidth=19cm]{geometry}

\begin{document}

hello world

\end{document}

Works perfectly. Can anybody tell me why it wouldn't work in my previous file?

Answer 1

From the geometry user manual (section 5.7 Other options):

pass

disables all of the geometry options and calculations except verbose and showframe. It is order-independent and can be used for checking out the page layout of the document class, other packages and manual settings without geometry.

Remove this from your options and geometry will set the page layout accordingly.