Hot pressed paper has a very smooth surface, produced by applying pressure and heat to the sheets.
Prior to mass industrialisation, paper had many different appearances and qualities. The high quality, expensive paper is an indicator of Caroline Bingley's position in society.
In a family of many daughters, it was customary that only the oldest girl would go out to balls and assemblies in order to prevent a younger sibling marrying the husband they might have otherwise snared.
As Charlotte will finally be married at 27, her younger sisters can hope to come out sooner than they thought.
In a world where women were not expected to work, nor respected if they did, the only way to ensure their future was to marry a financially secure man, regardless of his character.