[jQuery photo gallery]

Best solution I would suggest would be to go for a popular CMS like Joomla or Wordpress. There are dozens of great gallery components or plugins for each.

[photo gallery in php]

You can pick a CMS like Joomla or Worpress and install a Gallery plug in like phoca gallery for Joomla.

[The Simplest Possible Site - almost]

The simple linking may not always work if user has a adobe plugin installed in browser. It will then show the PDF inside the browser instead of giving the download prompt. You will need to add some htaccess directive in that case. Add the following in the .htaccess file on server.

<FilesMatch "\.(?i:pdf)$">

ForceType application/octet-stream

Header set Content-Disposition attachment

</FilesMatch>

[404 page not found.]

Yep. You need apache modrewrite module enabled for the htaccess in wordpress to work. Glad that you got it figured out.