I'm using this https://github.com/TomRoush/PdfBox-Android PDFBox on Android Studio library to extract text from a PDF document. Here's what I'm doing:
File pdf_file = new File(file_path);
to create the file, then
PDDocument document = null;
document = PDDocument.load(pdf_file);
to load the file into a PDDocument object, and then
PDFTextStripper pdfStripper = new PDFTextStripper();
pdfStripper.setStartPage(...);
pdfStripper.setEndPage(...);
String page_text = pdfStripper.getText(document);
to get the text content of the page. The issue is that when there's for example the word "firm" it displays it like "fi rm". It basically puts a space after fi (and I guess fls and other ligatures). I tried reading this Problems with extracting OpenTypeFont text using pdfBox but I don't understand how to fix it. There are no solution details.
Important: As it turns out, in my PDF file, I don't have any ligatures such as fi but I have regular fi and yet, there's space after it. A solution is unclear.
PDF file: https://wetransfer.com/downloads/09e9036dda4a7962ccad32b1cbcd8edc20200506050349/ab4752
The issue is that when there's for example the word "firm" it displays it like "fi rm".
The reason is simple: There is a space after the "fi"!
This is the text drawing instruction drawing the line with the first occurrence of "firm" in your sample file:
[( )360.3(Mr Dursley was the director of a “)250( )110.3(rm called Grunnings, )]TJ
The byte “ (147) by means of the font encoding is mapped to the glyph name fi and by means of the ToUnicode map of the font to the Unicode character U+fb01, the Latin small ligature fi.
Thus, PDF viewers display the ligature glyph fi and text extractors extract either the Unicode ligature character fi or after expansion the characters f and i.
After that ligature the start point for drawing the next glyph is moved left by 250 units, then a space is drawn, then the next start point is moved left by 110.3 units, and then "rm" is drawn.
Thus, you don't see a gap between "fi" and "rm" in viewers (because the moves left counteract the drawing of the space glyph) but text extractors extract a space character (because it's there).
You can check that this is not a PDFBox quirk, e.g. Adobe Reader with copy&paste extracts that text line as
Mr Dursley was the director of a fi rm called Grunnings,
Just like PDFBox it expands the ligature and extracts the space character.