We received this issue from a few users. So, We did a workaround and made a way to fix.

Some servers add spaces to uploaded files somehow, for encoding type I think but not totally sure. However, due to extra spaces, there’s a warning message displays on top of Viewer.

Warning: session_start(): Cannot send session cache limiter – headers already sent (output started at /home/xxxxx/public_html/wp-content/plugins/pdf-viewer-for-wordpress/web/viewer-shortcode.php:3)

And here’s how you can fix it:
1. Login to your wp-admin with admin user & password.
1. Install & activate Wpide plugin from Plugins->Add New
3. open plugins/pdf-viewer-for-wordpress/web/viewer-shortcode.php
4. replace first few lines with the following code:


***** For some cases, if you still having the issue after replacing lines, please try removing first two lines. that are :

ob_start();
session_start();


First few lines should look like this.

5. Do the same for plugins/pdf-viewer-for-wordpress/web/viewer.php
6. make sure there is no extra space on the first line before or after [ITS VERY IMPORTANT]
7. Save the Files.

The error should be gone now...

Please Contact Support if you still having the issue or need our help to get it done.

Thank You[/fusion_builder_column][/fusion_builder_row][/fusion_builder_container]