A Guide to the PDF Tools on Synthixx and What Each Does Well

Lists of the best free PDF tools tend to praise everything and mention no limits. This guide is narrower and more useful: it covers the PDF tools available on Synthixx, groups them by the job you are trying to do, and says plainly what each one is good for and where it falls short. It also lists what the site does not do at all, so you do not waste time looking.

How these tools work

All of the tools below run in your browser. The PDF is read and rewritten on your own device rather than sent to a server, which is why there are no accounts and no queues. The trade-off is that the tools rely on JavaScript libraries running in a browser tab. They handle everyday jobs well, but they are not a substitute for a full desktop PDF suite, and very large files depend on your computer's memory. One tool, OCR PDF, downloads language data from a public CDN the first time you use a language; the document itself stays local.

Combining, splitting and reordering

• Merge PDF joins several PDFs into one in the order you set. It joins pages as they are; it does not reduce size or fix inconsistent page sizes between the files.
• Split PDF divides a document by page ranges, and gives you a single PDF or a ZIP when the split produces several files. You need to know the page numbers you want.
• Extract PDF Pages pulls chosen pages into a new PDF, which suits sending only the relevant part of a document.
• Delete PDF Pages removes the pages you name and keeps the rest untouched; you choose pages by number, so check the page count first.
• Reorder PDF Pages rearranges page order, and it changes only the sequence, not page contents.
• Rotate PDF turns selected pages in 90 degree steps, which fixes sideways scans; it changes how pages display, not the underlying scan quality.

For a walkthrough of the most common job here, see how to merge PDF files.

Converting

• PDF to Word extracts the text of a PDF into a .docx; it does not rebuild layout, tables or fonts, and a scanned PDF gives nothing without OCR first.
• Word to PDF turns a .docx into A4 PDF pages; the pages are built from images of the rendering, so the text is not selectable.
• JPG to PDF and PNG to PDF place images onto PDF pages, useful for turning phone photos or screenshots into one document, though photo quality is only as good as the source.
• PDF to JPG and PDF to PNG render pages as images, which is handy for previews or slides, but the output is pictures, not text.
• Other converters, such as PDF to Excel, Excel to PDF and PowerPoint to PDF, follow the same principle: basic text and structure carry across, exact visual layout does not.

The reasoning behind those limits is covered in PDF vs Word: when to convert.

Forms, marks and page furniture

• Fill PDF lets you type into a form in the browser; it suits forms that already contain fillable fields.
• Flatten PDF turns form fields into fixed page content, so the entries can no longer be edited by the next person, though it is not a security feature.
• Sign PDF stamps a visual signature onto a page. It is a picture of a signature, not a cryptographic digital signature, so it carries no certificate.
• Add Page Numbers, Add Header and Footer and Add Watermark place text on every page; the text is drawn on top of the page, so plan for it not overlapping existing content.
• Crop PDF trims margins, and PDF Page Size Converter scales pages to a new paper size, fitting the content and centring it.
• PDF Metadata Editor and PDF Metadata Remover change or clear properties such as title and author. They do not touch the visible content.

Size and repair

• Compress PDF removes metadata and re-saves the file. It does not recompress images, so a scanned or photo-heavy PDF will often barely shrink. If you need a large reduction, the practical route is to reduce image size before building the PDF; see compressing a PDF without losing quality.
• Repair PDF attempts to rewrite a damaged file's structure; it can rescue some broken files but cannot restore content that is truly missing.

OCR and editing scanned pages

• OCR PDF reads scanned pages in the browser and gives you a TXT file, plus an English-only searchable PDF. It works best on clean, upright scans, is weak on handwriting, and does not produce Word files. More detail is in how to OCR a PDF.
• Document Editor changes text in Word files, PDFs and images while keeping the surrounding formatting. Font matching on scans and PDFs is an approximation, and its optional AI correction is the one feature that sends data off your device, after a confirmation.

What is not offered

Being clear about gaps saves time, so here they are.

• No password protection and no password removal. There is no tool to encrypt a PDF or unlock one.
• No digital signatures. Signing is limited to a visual stamp, and there is no certificate-based signing.
• No true image recompression in PDFs. Compressing removes metadata and re-saves, nothing more.
• No exact-layout conversion between PDF and Office formats. Conversions carry text and basic structure only.
• No Word output from OCR. OCR gives TXT and an English-only searchable PDF.

If any of those are essential, use desktop software built for them.

What to do

Start from the job, not the tool name. To assemble a document, merge, then reorder or delete pages. To make it smaller, expect modest gains from Compress PDF and consider the source images instead. To edit text, decide between converting and editing in place. For scans, run OCR before anything that needs real text. Whatever you choose, keep your original file until you have checked the result.