-
InfluxDB
Power Real-Time Data Analytics at Scale. Get real-time insights from all types of time series data with InfluxDB. Ingest, query, and analyze billions of data points in real-time with unbounded cardinality.
If you can program in Java then Apache PDFBox is an excellent very high quality library for reading (and writing) PDFs.
Another possibility is MuPDF. There are bindings for many platforms and languages.
NOTE:
The number of mentions on this list indicates mentions on common posts plus user suggested alternatives.
Hence, a higher number means a more popular project.