Tika's PDF text extraction is fine if you're just trying to get searchable text. Which is what it's made for: Slurping doucments into Lucene. Fulltext search typically isn't terribly sensitive to getting the order of words right, and is even less sensitive to getting the formatting right.

If you're trying to get something fit for consumption by human (including via a screen reader) or an NLP pipeline, though, all the problems discussed in that FilingDB article still apply.

aspose can convert pdf to html

Firefox's PDF reader does the same. A few years back, I wrote wrote a pdf to csv converter with selenium -- it worked surprisingly well! Though, after I finished I found tabula and the code became immediately useless, hah.

When that happens to me, it's due to a keyword I hadn't thought of looking for. Then, while building the project, it came to me.

I used Tika to build a search engine prototype, and it was fantastic for getting us up and running quickly.

It's a really easy to use generic parser for a bunch of document types. The downside of being so generic and easy to use is that you end up lacking document-specific context that could be useful. For example: Do you consider the header/footer text to be important, or just noise (Page 1, Page 2, etc.)? Is the text contained in the Table of Contents or section headers important, or just the actual content? You won't find any ways to tweak the result, which could be a good or bad thing depending on your use case.

We ended up using it as our "fallback" parser, writing more contextually aware ones for document types of greater importance to our use case (PDFs were high on the list).

so how did u do to understand the "form" of the document such as table of contents and co.

For reference, it's https://news.ycombinator.com/item?id=24460142 ; https://filingdb.com/b/pdf-text-extraction

I’ve found Tika’s PDF to HTML parser to be pretty good. My only complaint is that in a double spaced document where there is equal amount of space between paragraphs and normal lines, it labels every line as a separate paragraph.