Everything redirecting to index.php but still direct access to PDF's

I have a PHP-Project, where I am redirecting every URL to index.php. But the files in uploads folder (.png, .pdf, etc.) can be accessed directly. Is there a way to prevent this and also redirect URLs like https://example.com/uploads/asdf.pdf to index.php.

This is my .htaccess file:

AddType application/x-httpd-php .html
RewriteEngine On
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^(.*)$ index.php [L,QSA]
RewriteRule ^([^\.]+)$ $1.php [NC,L]

Made some changes on the .htaccess file, but did not help.

Solution

RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^(.*)$ index.php [L,QSA]

To rewrite all requests that do not map to physical files OR that map to .pdf files in the /uploads directory to index.php then you can basically just add an additional OR'd condition to the above rule.

For example:

RewriteCond %{REQUEST_URI} ^/uploads/[^/]+\.pdf$ [OR]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^ index.php [L]

So, the above states that any request of the form /uploads/<file>.pdf (regardless of whether that .pdf file exists or not) OR that does not map to a physical is rewritten to index.php.

If you wish to rewrite everything in the /uploads directory through index.php then simply change the regex from ^/uploads/[^/]+\.pdf$ to ^/uploads/.

I also simplified (and made more efficient) the regex in the RewriteRule directive (since you don't need to match and capture everything) and the QSA flag was redundant here.

UPDATE:

How is it possible with files, which are in a subfolder of the uploads folder?

You can tweak the regex in the preceding condition (RewriteCond directive). For example...

A specific subfolder of the uploads folder:

RewriteCond %{REQUEST_URI} ^/uploads/subfolder/[^/]+\.pdf$ [OR]
:

Any subfolder of the uploads folder:

RewriteCond %{REQUEST_URI} ^/uploads/[^/]+/[^/]+\.pdf$ [OR]
:

Any .pdf file under the /uploads folder (including any subfolder):
```
RewriteCond %{REQUEST_URI} ^/uploads/.+\.pdf$ [OR]
:
```

See the following question for details on regular expressions (regex):
Reference - What does this regex mean?