Install the necessary packages into the virtual machine with:
!apt-get install texlive texlive-xetex texlive-latex-extra pandoc
!pip install pypandoc
Mount your google drive to get access to your ipynb files
from google.colab import drive
drive.mount('/content/drive')
I had to copy the files from the drive to the working directory, because the drive is/was mounted as read only.
!cp drive/My Drive/Colab Notebooks/example.ipynb ./
Then you can run the converter.
!jupyter nbconvert --to PDF "example.ipynb"
Then you can download the file in the left side panel or through running this cell
from google.colab import files
files.download('example.pdf')