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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.
Just reader this: SumatraPDF. It's very fast.
Not sure how good it is for privacy, but it is opensource and I use it a lot - PDFSam https://pdfsam.org/
Or pdftk. Or Okular. There are many FLOSS options besides using the last free version of some random paid editor.
NOTE:
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Hence, a higher number means a more popular project.