The file PDF is a final format, meant to be used after all changes are finished. This means that unlike .doc e .xls, it does not contain all that is needed for the subsequent modification of the file, at least in the most common form that we are used to using.
The solutions that we can find on the net often do not allow us to carry out complex operations, or they prove to be laborious to use. Many just try to roughly discover the structure of a document using a principle similar to the one our scanner software uses when we try to scan a document.
Therefore, unless the source file is available in another form, the results obtained are intended to be approximate. Fortunately, the Open Source world offers a not perfect solution but completely free. The packages for the office libreoffice e OpenOffice.org. In addition to allowing us to save in PDF format, they have an extension designed specifically for opening this type of documents.
The two packages are very similar, and in both cases we have to open the main screen of the program, without choosing any specific application, and directly drag the file we want to modify from an Explorer window to the screen.
The package will take care of transforming the file and suggesting the most suitable program for editing.
Two other online solutions that I suggest are:
If you know other solutions they are welcome ..