You don't need a dedicated program to see a PDF's contents - just open and view the file in your browser. However, if you want to make changes, you'll need specialist editing software. We check out six free tools that let you tweak text and images in PDFs.
1. Apowersoft Online PDF Editor
Apowersoft's PDF Editor comes in two flavors: an online version and a free download. We recommend using the online version because the free download stamps your PDFs with a watermark.
Using the online version requires that you download a launcher, so it doesn't feel like an online tool in the traditional sense that you need to access it in a browser. We loaded some complex PDFs into the software and it immediately discovered the text (even text in unusual fonts) so we could get on with editing it.
The tool is adept at distinguishing tricky elements such as images placed in layers and allowed us to move and remove them. All this is done by simply clicking the Edit button at the top and selecting the element you want to change.
It can't edit absolutely everything - we found a few fonts that it couldn't handle and it wouldn't work on text that had been rotated. It also failed to edit the images in some documents - we suspect it depends on how the original designer has saved the file. But don't let these minor setbacks put you off - there are still plenty of things you can do with this software.
At a document level, you can remove pages and insert new pages. You can also create PDFs from scratch, though it's not ideal for this because it doesn't have enough layout tools. Also, it uses American paper sizes, so you'll need to set the size of an A4 PDF manually.
2. PDF-XChange Editor
PDF-XChange Editor provides both free and paid-for versions, but its website reassuringly claims that 60% of the tools in the full version are active and usable in the free one. Unfortunately, some of that missing 40% affects the editing sphere so while you can, for example, edit text for free, making other changes - such as manipulating images or other features or adding new pages - will leave your saved version stamped with a watermark.
Nevertheless, we were impressed with the power of the text editing, which was able to tackle some text items that even the award-winning Apowersoft tool couldn't make changes to.
The interface will look reassuringly familiar to anyone who's used a Microsoft Office program in the last decade. The tools are laid out in a ribbon toolbar that's very easy to find your way around, even when you're first getting to grips with the program.
3. Sejda PDF Editor
Sometimes, all you want to do is make a small change to the text of a PDF file, such as correcting a typo in your otherwise carefully crafted document. In such cases, having to download a whole program seems like overkill, and you can just as easily do the job using a browser-based tool.
Sejda PDF Editor might be all you need. Most of the things it can do are concerned with adding elements to your PDF, such as extra pages and images - so long as you're happy for them to lay on top of the existing contents. If you need to block out a whole section, for example, this tool could handle that easily.
There's also a text-editing tool that did a surprisingly good job of detecting fonts and letting us edit the text in place.
4. Icecream PDF
Icecream PDF Editor's clean interface is very easy to use - simply click an element to edit it and make your changes. Unfortunately, the execution isn't quite as clean - some changes we made to documents didn't pick up the correct font and defaulted to a basic Windows version, which was disappointing.
5. pdfFiller 
This online PDF editor works with files of up to 25MB in size. Because it's online, you have to first upload your PDF to the site, so it's not as immediately usable as a downloaded program. Once that's done, though, just switch your browser to full screen and it's just like any other software. It wasn't so good at replacing unusual fonts, though, and switched them instead for similar-looking alternatives.
6. PDFescape 
This online editor is designed to accompany a more sophisticated paid-for program, and we found the tool had been pared-back too far. You can add elements - images, text boxes, and even more complex additions such as forms - to a page, but you can't edit what's already there without upgrading to the paid-for version.
