PDF Viewing Hardware
So called e-Reader devices have been available for many years, most notably Amazon's Kindle range of products. In general such devices are targeted at consumers for reading of ePUB-format publications rather than PDFs. A list of such devices and a summary of their functionality is provided on Wikipedia.
Recently, with the improvements in display technology and pen devices, a number of specialist devices for document display and markup have been developed. These devices tend to provide an electronic equivalent to paper, providing very clear display of text and graphics, with markup provided using a digital pen. Many of these devices rely on so-called E Ink technology, developed from 2008 onwards, initially in the USA.
Devices like ReMarkable and PocketBook are essentially paper replacements, with limited functionality beyond the display of selected file formats, and often in mono (i.e. no color). Amazon's more recent range of Paperwhite Kindle hardware is similar, but with much broader functionality. Devices of this type focus on the quality of digital reading experience, markup and data sharing. As such they require that a specific range of non-protected file formats are used, which includes unprotected PDF documents amongst others. The majority of specialist document reading devices are designed for ePUB format files rather than PDFs, and most of these do not support the display of standard (non-DRM) PDF files, although some support specific DRM services (e.g. Adobe, Amazon, Barnes and Noble, Readium LCP).