Guides
Working with documents, honestly explained.
How PDF operations actually work, what can go wrong, and how to keep sensitive documents private. More guides arrive as the tools they describe ship — never before.
Organize & convert
- Merge PDF files free — no account, no limitMerging PDFs is a simple operation that should not require an account or subscription. This guide covers the best free options and how to merge PDFs correctly.7 min read
- Convert HEIC to PDF on iPhone — no app needediPhones save photos in HEIC format by default. Here is how to convert HEIC images to PDF using only built-in iOS features, no third-party app required.6 min read
- Excel to PDF: why most converters break your layoutExcel layout problems in PDF output come from specific causes. This guide explains what breaks during Excel-to-PDF conversion, how to prevent it, and how Filum draws your spreadsheet's stated layout in your browser.7 min read
- Convert JPG to PDF — combine photos into a single documentConvert one or more JPG images to PDF online without uploading. Your photos are arranged on A4 pages and packaged into a single PDF, entirely in your browser.3 min read
- Split PDF — extract pages without uploading your fileSplit a PDF into individual pages or extract a range of pages entirely in your browser. No upload required — your document never leaves your device.3 min read
- Rotate PDF pages — fix orientation without uploadingRotate PDF pages 90°, 180°, or 270° directly in your browser. Fix portrait-to-landscape orientation issues on individual pages or the whole document, with no upload required.3 min read
- Reorganize PDF pages — delete, reorder, and rearrange without uploadingDelete unwanted pages, drag to reorder, and download the result — all in your browser. Your PDF is never uploaded. No account required.3 min read
- Converting PowerPoint to PDF, and where fonts break itWhy a deck converted to PDF can re-flow its text, what a metrically compatible font substitute does about it, and what cannot be drawn from a .pptx without a copy of Office.5 min read
Edit & annotate
- How to crop a PDF (without uploading it)Crop the margins or borders off a PDF's pages in your browser — losslessly, without uploading the file. How cropping works, why it's not the same as redaction, and how to do it on every page at once.4 min read
- Edit a PDF online — what you can and can't change (and how)Practical guide to editing PDFs online: sign, fill forms, organize pages, redact, watermark, and more — all without uploading your document. Honest about what 'edit' means.4 min read
- How to edit a PDF free — add text, highlights & drawings, no uploadEdit a PDF entirely in your browser: add text, highlight passages, draw freehand, and box anything on any page. Nothing is uploaded, and every existing page stays exactly as it was.6 min read
- Watermark a PDF — stamp text across every pageAdd a text watermark (DRAFT, CONFIDENTIAL, your company name) to every page of a PDF. This guide covers watermark positioning, opacity, and what watermarks actually prevent.3 min read
- Redact a PDF — permanently remove sensitive textPermanently remove sensitive text and images from a PDF. This guide explains the difference between real redaction and just covering text, and how to verify redaction worked.4 min read
- Fill out a PDF form online — type into fields without printingFill in PDF form fields directly in your browser without printing or scanning. Works with standard AcroForm fields: text boxes, checkboxes, radio buttons, and dropdowns.3 min read
- Add page numbers to a PDF — place numbers on every page in secondsAdd page numbers to any PDF in your browser — choose position, size, and starting number. Runs on-device: your file is never uploaded.3 min read
- Flattening a PDF: what it locks and what it does notFlattening turns form fields and annotations into page content. Here is what that protects against, what it does not, and why some annotations cannot be flattened.4 min read
- Comparing two versions of a PDFA word-level diff plus a visual change measure, why comparison is the one operation that exposes two confidential files at once, and what page-position matching cannot do.4 min read
PDF output
- How to convert PDF to Word without losing formattingFormatting loss in PDF to Word conversion is caused by specific technical limitations, not converter quality. This guide explains the causes and how to get the best results.8 min read
- Why your PDF to Word converter is destroying your formattingPDF-to-Word formatting problems are caused by specific technical factors. This guide explains what happens inside a converter and which problems can be avoided.7 min read
- How to compress a PDF without losing qualityPDF compression reduces file size by removing data. This guide explains which data is removed at each quality level and how to compress while preserving what matters.6 min read
- PDF to image: JPG vs PNG vs WebP — which to chooseTurning a PDF page into an image means picking a format. A practical comparison of JPG, PNG, and WebP on file size, sharpness, and compatibility — with measured numbers.5 min read
- OCR a PDF online — extract text from scanned documentsRun OCR on a scanned PDF to extract searchable, selectable text. This guide explains how OCR works, what affects accuracy, and when online OCR is the right tool.4 min read
- Repair a corrupted PDF — recover files that won't openFix a PDF that won't open or displays errors. This guide explains what causes PDF corruption, what can be recovered, and when a file is unrecoverable.4 min read
- Convert PDF to Markdown — structured text for docs, LLMs, and editorsConvert a PDF to Markdown in your browser. Headings, paragraphs, and bold are preserved from the text layer. Useful for documentation, LLM prompts, and content migration.3 min read
- Convert PDF to PowerPoint — without uploading your deck anywhereTurn every page of a PDF into a PowerPoint slide, entirely in your browser. The page's own graphics, with its text rebuilt as real PowerPoint text you can retype. Your file is never uploaded.5 min read
- How to convert PDF to Excel — what works, what doesn't, and whyConvert a PDF's tables to an editable Excel spreadsheet without uploading the file. This guide explains what PDF-to-Excel actually does, when it works well, and when you'll need to clean up the output.4 min read
- How to convert a PDF to JPG — free, on-device, at 300 DPIA PDF does not become a JPG by saving it differently — each page is rendered into an image at a set resolution. Here is what that means, how to pick the right DPI, and how to do it without uploading your file.4 min read
- What is PDF/A and how to convert your PDF to itPDF/A is the ISO standard for archiving PDFs in a self-contained format. This guide explains what it is, when you need it, and how to convert your PDF to PDF/A without uploading to a third-party service.4 min read
- PDF to PNG, and when lossless is the right choiceWhat DPI actually means when converting a PDF page to an image, when PNG beats JPG, and how to check that the resolution you asked for is the resolution you got.4 min read
- Getting the text out of a PDFWhy some PDFs give up their text instantly and others give nothing, how to tell which you have, and why an empty download is the wrong answer to a scan.4 min read
- Extracting the images a PDF actually containsThe difference between a picture of a page and the photo placed on it, why JPEGs can come out with zero quality loss, and why a partial result must be reported.4 min read
Images & graphics
- How to compress an image without wrecking itWhy images are so much bigger than they need to be, what compression actually removes, and how to pick a setting that shrinks the file without a visible change.5 min read
- How to resize an image and keep it sharpWhy resized images go soft or jagged, what a good resampling filter does differently, and how to hit exact pixel dimensions without destroying the picture.5 min read
- How to crop an image to an exact regionCropping to the pixel, why phone photos crop wrong in some tools, and what a crop does to image quality — including the case where it should do nothing at all.4 min read
- JPG, PNG, WebP, AVIF — which image format to convert toWhat each image format is actually good at, when converting is worth it, and the two conversions that quietly damage your file if you are not paying attention.6 min read
- Rotating a JPG without losing qualityMost tools re-compress a photo every time you turn it. There is a way to rotate a JPG that changes nothing else at all — here is how it works and when it applies.5 min read
- How to watermark a photo, and what a watermark can actually doWatermarks deter casual reuse rather than prevent theft. Here is how to place one that survives a crop, and why the images worth watermarking are the ones worth not uploading.4 min read
- How to blur a face, a plate, or an ID in a photoBlur versus pixelate, why some blurs can be reversed, and why a tool that hides sensitive parts of a picture should not be sent the un-hidden version first.5 min read
- Making a meme from your own photoClassic top-and-bottom captions, why the black outline exists, and why the photos people caption are exactly the ones they should not be uploading.3 min read
- How to add text to an image and keep it readablePlacing labels on a photo so they stay legible over any background, keeping the file in its original format, and doing it without sending the picture anywhere.4 min read
- Removing an image background, and what the model can and cannot doHow automatic background removal actually works, why hair and glass are hard for every tool, and what it means to run the model on your own device instead of a server.5 min read
- What image upscaling can and cannot recoverThe honest limits of AI upscaling: what a super-resolution model adds, why blurry photos stay blurry, and how a 4× enlarger runs in a browser instead of on a server.5 min read
- Extracting text from a photo, and why it sometimes failsHow OCR reads a photograph, what makes an image readable or not, and why a tool that returns an empty file instead of an error is worse than useless.5 min read
- Converting SVG to PNG at the size you actually needWhy an SVG can be rendered at any resolution for free, the 300-pixel default that silently ruins conversions, and what happens to fonts, scripts, and linked images.5 min read
- Converting SVG to JPG, and when you should notJPEG is the wrong format for vector art in most cases. Here is when it is genuinely required, what happens to transparency, and how to get the best result anyway.4 min read
- Which favicon files a site actually needs in 2026The modern favicon set is smaller than the twenty-file packages suggest. What each file is for, why iOS icons go black, and the markup that makes any of it work.5 min read
Security & privacy
- The privacy problem with online file convertersOnline PDF converters handle sensitive documents but rarely explain how long they retain files or what they do with them. This guide explains the risks and how to evaluate a converter's privacy model.7 min read
- How to sign a PDF online for free — no upload requiredMost PDF signing tools upload your document to a server. This guide explains how to sign a PDF free online without giving up your document.5 min read
- Password protect a PDF — add encryption that actually worksAdd a password to a PDF so it can only be opened by people who know it. This guide explains PDF encryption, password strength, and what protection actually prevents.4 min read
- Remove a PDF password — unlock a PDF you ownRemove the password from a PDF file you own so it opens without prompting. This guide explains when unlocking works, when it doesn't, and the difference between open and permissions passwords.3 min read
- What your PDF is telling people, and how to remove itPDFs carry author names, software fingerprints, timestamps, and XMP blocks. Here is what is in there, why deleting it is harder than it looks, and how to verify it is gone.5 min read
Context & comparisons
- PDF tool credit limits — why they exist and how to finish your workHit a credit limit on your PDF tool? This guide explains why credit systems work the way they do and which alternatives let you convert files without counting credits.6 min read
- PDF tool rate limits — why they exist and how to work through a batchHit an hourly rate limit on your PDF tool? This guide explains why per-hour limits work the way they do and which alternatives handle PDF conversion without hourly caps.7 min read
- Best free PDF converter with no sign-up requiredThe best free PDF converters work without an account — and the strongest never upload your file at all. A practical comparison on privacy, limits, and what each one actually covers.6 min read