[SalesForce] Visualforce page title is not set

You won't be able to ignore the Salesforce CSS as it will be loaded by the browser and thus used whenever there is a class that matches the name.

You don't need to use an <apex:stylesheet /> tag to include a stylesheet in your page, you can just use a regular tag. This isn't supported by the specification, but browsers will accept it.

You could also put the styles directly in the page, which again isn't supported by the specification but the browser will accept it, or use the HTML5 scope attribute on a mid-document style. You do lose the benefits of CSS this way though, as the styles are in the page and thus not cached or reusable. It looks like browser support is pretty patchy for this too.

Adding !important to your styles is a potential way to ensure that your styles have precedence over the Salesforce styles regardless of order, but there are a couple of downsides:

1. This tag was introduced as an accessibility feature to allow users with particular needs (e.g. large fonts due to impaired vision or different colour combinations due to colour blindness) to apply their preferred styles to a page, so your important styles could well break the page for them.
2. Its more difficult for someone to customise the style on your page - for example, they add a style class to the page but it has no effect because somewhere in a stylesheet the important tag has been used and that takes precedence.

The way I tend to approach this though is to use JavaScript to append my tag to the existing ones, typically through the jQuery method outlined in the answer to this question:

https://stackoverflow.com/questions/12093509/jquery-add-css-to-head

It is a common assumption that the HTML to PDF engine presently used by Salesforce is Flying Saucer that only supports version 2.1 of CSS (W3C Recommendation 07 June 2011) whereas SLDS is designed to work with modern browsers only that support version 3 CSS.

So while you may be able to eventually get some parts of the SLDS markup to work, the PDF output is unlikely ever to be as you would like it to be. Including simple CSS used just for the PDF output is the simplest workaround.