Improper text selection (selection position offset) during multi-page view (Odd or even spreads)

[AesaraB]

Attach (recommended) or Link to PDF file here: Pages removed to avoid copyright issues, issue still reproducible here

Configuration:

• Web browser and its version: 89.0.1
• Operating system and its version: Windows 10 build 19041.1052
• PDF.js version: 2.9.45
• Is a browser extension: No

Steps to reproduce the problem:

1. Open the attached document.
2. Attempt to select text to observe correct behaviour.
3. Select a multi-page view from the pdf.js viewer.
4. Attempt to select text to observe improper behaviour.

What is the expected behavior?

What went wrong? Attached Below

[AesaraB]

The offset text appears to use a positive value for the Left property, instead of a negative one. This positive Left is indeed correct when in single-page view, but when in multi-page view it becomes evident that the inverse of the quantity properly aligns the text. As seen above, the offset doesn't seem to be relative to the viewer or absolute to the document body, as the same right-leaning offset occurs on the right page.