Knowledge base

What a PDF file is, how it works inside, when to use it, and how to compress, merge, edit or convert PDFs without uploading them to any server.

What a DOCX file is, how it differs from the old DOC and from PDF, and how to open it, repair it or convert it to PDF without losing formatting.

What an Excel XLSX file is, how it stores sheets and formulas, its limits, and how to convert it to PDF or repair it without uploading it online.

What a PowerPoint PPTX file is, how it is built, why it gets so big, and how to convert it to PDF so you can share it without the layout breaking.

What a JPG or JPEG file is, how it compresses photos with quality loss, when to use it, and how to cut its file size without a visible drop in quality.

What a PNG file is, why it supports transparency without losing quality, when to choose it over JPG or WebP, and how to reduce its file size.

What WebP is, Google's image format: how much it saves versus JPG and PNG, what it supports, and how to convert it so it opens anywhere.

What a GIF file is, why it's still used for short animations, its 256-color limit, and how to cut its file size or replace it with something better.

What a BMP file (Windows bitmap) is, why it's so big, when it's still used, and how to convert it to JPG or PNG so you can share it easily.

What a TIFF file is, why it's used in scanning, professional photography and printing, and how to convert it or reduce its size so you can share it.

What is a TXT file? Learn how UTF-8 encoding works, why accented characters break, and when plain text beats PDF or Word.

What is Markdown? Learn how to write it, what .md files are for, and how to turn your notes into a PDF or web page without hassle.

What is HEIC, the iPhone photo format? See how it compares to JPG, how to open it on Windows, and how to convert it to JPG or PDF.

What is an SVG file? Learn how vector graphics work, when to use them instead of PNG or JPG, and how to convert them to PDF.

What is a CSV file? Learn how to open it in Excel without broken accents or columns, and when to choose it over XLSX or PDF.

What is an ODT file from LibreOffice? See how it compares to DOCX, how to open it in Word, and how to convert it to PDF with no formatting loss.

What is an EPUB? Learn how reflowable ebooks work, how EPUB differs from PDF, and how to read it on your phone, tablet, or computer.

What is HTML, the language of web pages? Learn how it works, its history, and how to save a web page as a PDF without messing up the layout.

What is OCR? Learn how it turns a scan into selectable text, what image quality it needs, and how to get better results from your PDFs.

What is metadata in a PDF or photo? See what personal information it can reveal and how to remove it before sharing a file.

What a tagged PDF is, how it guides screen readers, and how to check whether your PDF has an accessible reading structure.

What PDF/A (ISO 19005) is, how PDF/A-1, A-2, A-3 and A-4 differ, and when you are required to use this long-term archive format.

What a PDF text layer is, why it lets you search and copy text, how OCR adds it to scanned files, and which operations remove it.

Scanned PDF vs. native PDF: how to tell them apart, why some can be copied and others cannot, and what to do with each type.

How lossy and lossless compression work, what you give up with each, and how to reduce the file size of a PDF or an image.

What DPI is and how much resolution you need to scan, read on screen, print or run OCR, plus how resolution affects file size.

What PDF encryption is, the difference between an open password and a permissions password, and what a password really protects.

Electronic signature vs. digital signature vs. visual signature on a PDF: what sets them apart and when each one is enough.

What a watermark on a PDF or image is, what it is for, how to place it well, and why it is not real technical protection.

What flattening a PDF means, what gets locked in (signatures, annotations, forms), what you lose, and when to do it in your workflow.

Permanent PDF redaction: why a black box is not enough and how to truly remove sensitive data from a PDF before you share it.

On-device file processing: what it means when your PDF is never uploaded to a server, the privacy benefits and its real limits.

RGB vs CMYK explained: when to use each color model for screen or print, and why your colors change when you print a PDF.

Vector vs raster graphics: the differences, pros and cons, and when to use each one for logos, photos and PDF documents.

Fillable PDF forms explained: what form fields are, how to fill them, why entries sometimes don't save and how to flatten a form.

Embedded fonts in a PDF: what it means, why they keep your text from changing typeface, and how to fix odd characters or empty boxes.

PDF password and permissions explained: open password vs. restrictions on printing, copying or editing, and how to manage each one.

Paper sizes A4, Letter and Legal: exact dimensions, differences, which to use and how to keep your PDF from being cut off when printing.

PDF links and bookmarks: how hyperlinks and the sidebar outline work, why they break when you edit a PDF and how to keep them intact.

Linearized PDF (Fast Web View): what it is, how it shows the first page before the download finishes and when it's worth using.

PDF page orientation and rotation: portrait vs landscape, why a scan comes out sideways and how to rotate PDF pages correctly.