The Hong Kong Public Libraries (HKPL) offer e-book borrowing via the "HyRead" or "SUEP" apps. While full Pearson textbooks are rare, supplementary "Mathematics in Action" workbooks might be available.
For students and educators looking for digital versions or supplementary materials: Junior Secondary Maths in Action 2A | PDF - Scribd Junior Secondary Mathematics In Action 2a Pdf
Since you specifically need the legitimate PDF, here are the official channels: The Hong Kong Public Libraries (HKPL) offer e-book