

Firefox can do basic annotating, adding text and adding pictures but it can’t make a new PDF from scratch.
You may be confusing Adobe Acrobat Reader with Adobe Acrobat? Full Acrobat is the proprietary tool to make a PDF file from scratch including some of the more complex functions.
PDF is an open standard and has been for a while, so there are now plenty of alternatives for most of the functions. LibreOffice Draw and Inkscape can do a lot of PDF creation functions but not all. There are also “print to PDF” options to create basic PDF documents too.
However some of the more niche functions are not widely supported or well supported; and there isn’t really any opensource dedicated PDF maker that I’m aware of. Layout tools are abundant but I think it’s things like building forms and document signing that is less easily replicated. There is Master PDF - a fully functional PDF maker which is proprietary and available for Linux; it $80 for a perpetual license. I’m not aware of any other alternatives myself.
I’m not sure this true - PDF is an open standard. The issue isn’t generally with layout and reproducibility - a good PDF maker and a good reader will give you an accurate representation of how it looks on all devices once the PDF is created.
Certainly there isn’t a dedicated FOSS tool for make PDFs; Libre Office and Inkscape do a decent job but not perfect which may be what you’re referring to. And they’re not dedicated PDF makers plus the real problem is building fillable forms and signature tools.
But there is a proprietary alternative called Master PDF that is a dedicated and supports all the PDF standard features I believe; one perpetual license is $80 compared to Adobe subscription based charging. I’m not aware of other options myself but they may exist. But it’s a viable alternative to the “adobe tax”.
Also of course if you have Office 365 from Microsoft, you can use Word to export docs to PDF reliably (in my experience). Obviously as far as you can get from FOSS, but it is an option on Linux via web browser if you have it from work for example; at least you don’t have to pay Adobe but it’s scraping the bottom of the barrel for this threat I know!