Delay in showing PDF file

[Daniel Gunawan]

A little bit more complicated than the title suggests...
Basically I have an app that allows the user to view the PDf version of a report.
If the file doesn't exist or older than the data, create the PDF file first, store it in the file system, before sending it to the browser.
The problem is, after the app creates the new file and stores it to the file system, the browser only shows a blank page. Only after a refresh does the PDF file shows up.
The above only happens if the file has to be created first before being sent to the browser. Existing files work perfectly.
How to make sure that the browser shows the PDF file everytime regardless whether it is an old or new file? A sleep()?
TIA