Hi @agarg, thanks for your post and thank you @Shira M for your support!
Just chiming in since indeed, cropping to content would be a great approach here when exporting your document to PDF, as per this section of our Help Center article.
However, if you would like to give your pages the same format initially, this has to do with document and page settings. To edit that, please head to File > Settings > Document settings > Canvas and page > toggle off ‘Infinite canvas’. From there, you can change the format and various other settings which will ensure identical sizes to your various documents when changed accordingly. For more information on this, I suggest going through our Adjust document and board settings Help Center article.
Hope this helps!