How to smart read PDF files in android on a mobile screen?
You can use @Voice Read Aloud app from the Play Store. Using @Voice Read Aloud app you can read aloud the text displayed in Android apps, e.g. web pages, news articles, long emails, TXT, PDF, DOC, DOCX, RTF, OpenOffice document files and more.

Note: You need Text-To-Speech engine and voices installed on your device to use this app. You may use more than one if you want.