I realized that the method mentioned above enables us to install the "ezPDF reader" app into IQ, which is orginally designed for 2.1 or 2.2 OS.
The ezPDF reader is almost perfect, in my opinion. It supports a perfect tap-to-zoom function which makes the screen width fit well with text parts. Moreover, it also supports a book-like page turning. It looks really nice
But, with large sized PDFs it's quite slow as it's not designed for 2.0 OS.
PS. One more function I forgot to mention.. It supports 'night mode' reading in PDF.