PDF pro version Search does not find any results

I’ve purchased the Pro version of the plugin to be able to SEO integrate the manuals, but it cannot find and text (even though I can search text in standard pdf readers). 
Here’s two examples of pdf’s that were crawled “with no readable text” (yes, I’ve recrawled them after purchasing the pro version):

https://teleguru.pl/telefony/huawei-p9/instrukcjaobslugi

For this manual it found text, but as you can see if you try to search – only a few words in the entire pfd file:
https://teleguru.pl/telefony/huawei-p8-lite/instrukcjaobslugi
Is there any bug with the crawler or am I doing something incorrect?

Kind regards,
Filip