Some of Librera reader main features include
Easy document discovery with optional and configurable lists
• Auto-Scan (with user selected folders)
• Browse (with an in-app file explorer)
• Recent (with a progress percentage bar)

• Support for bookmarks, annotations, and quick-jump contents
• Individually configurable Day and Night modes
• Support for many popular translators and offline dictionaries
• Vertical scrolling lock
• Auto-centering of documents
• Single page view of dual paged documents
• Music mode with configurable scrolling speed
• Voice reading capability (via TTS Engine or "text to speech")
• Fast and easy document searching
• ​Word search in multiple documents
• Online document format conversion
• Opening of files directly from archives (.zip)
• ​Right​ ​to​ ​left​ language support ​(Thai,​ ​Hebrew,​ ​Arabic, etc.)
• Continue reading from where you left off
• Online Catalogs (OPDS), search and download books
• Much, much more…

With Librera Reader, you can easily create self-maintained libraries of all your documents by specifying which formats to include and which folders to scan.
All document collections can be viewed in either a list or grid pattern.
Documents are easily identified by -adjustable thumbnail covers and detailed descriptions.
Your library can be sorted by path, name, , or date and, there is a filter to help locate specific documents or document groups.

While reading, documents can be locked into a vertical only scrolling mode and can be set to either page or screen flipping.
Text can be reflowed and annotated. Volume keys can be configured for scrolling and backgrounds customized.
Excerpts can be translated, shared, copied, and searched on the internet.

System Requirements:
Requirements: Android 4.4+

Home Page - https://play.google.com/store/apps/details?id=com.foobnix.pro.pdf.reader&hl=en