You have probably clicked through a dozen links from Libgen, Scribd, or obscure Blogspot pages. Here is why the "Lihim na Karunungan PDF" is notoriously difficult to get working.
Solution: Use Adobe Acrobat’s "Enhance Scans" tool or free online OCR tools. Lihim Na Karunungan Pdf WORK
Forget random blogspot sites. Go directly to Archive.org. Search for: You have probably clicked through a dozen links
Several users have uploaded cleaned-up versions. Look for files labeled: Several users have uploaded cleaned-up versions
Warning: Even on Archive.org, some scans are from microfilm and are inverted (white text on black). That is still "working," just tricky to read.