PDF tasks come up constantly — merge a scanned invoice with a contract, extract two pages from a 40-page report, compress a file to email it, fill in a form, add a signature. Adobe Acrobat handles all of this, but at $20+/month it's overkill for occasional use. Here are the free tools that do each job cleanly, without watermarking your output or demanding a subscription.
Merging and Splitting PDFs
PDF24 (browser + free desktop app)
pdf24.org is one of the most capable free PDF suites available. The browser version handles files locally in your browser — they don't touch a server. The free Windows desktop app is fully offline with no watermarks and no usage limits.
Supported tasks: merge, split, compress, rotate, reorder pages, convert to/from Office formats, OCR, add passwords, remove passwords, extract images.
Smallpdf (online, limited free tier)
smallpdf.com has a polished interface and handles most tasks well. The free tier allows two tasks per day, which is enough for occasional use. Output has no watermarks even on the free plan.
Compressing PDFs
Large PDFs are usually large because they contain unoptimized images. Compression tools re-encode those images at lower quality.
ilovepdf.com — Compress
ilovepdf.com's compression tool offers three levels (extreme, recommended, less compression). The "recommended" setting typically reduces a 10 MB scan to 2–3 MB with no visible quality difference at normal viewing size. Free with no watermarks; uploads go to their servers.
Ghostscript (command line, fully offline)
For power users or batch processing, Ghostscript (free, open source) compresses PDFs aggressively from the command line:
gs -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 -dPDFSETTINGS=/ebook \
-dNOPAUSE -dBATCH -sOutputFile=output.pdf input.pdf/ebook targets 150 DPI (good for screen); use /screen for 72 DPI or /printer for 300 DPI.
Filling PDF Forms
Many PDFs with form fields are "flat" (non-interactive) scans that don't allow typed input. For interactive forms, your browser's built-in PDF viewer can fill and save most of them — try dragging the file into Chrome or Firefox before reaching for a third-party tool.
PDF24 form filler
For non-interactive (flat) forms, PDF24's "Fill PDF" tool lets you position text boxes, checkboxes, and signatures anywhere on the page. It works in-browser with no upload for small files.
Signing PDFs
DocHub (free tier: 3 documents/month)
dochub.com provides a clean interface for drawing, uploading, or typing a signature onto a PDF. Three documents per month free, no watermark. Suitable for occasional contracts.
Smallpdf e-Sign
Covered by the same free two-tasks-per-day limit. Draw or upload a signature image, position it, and download. Simple and clean.
Built-in on macOS
If you're on Mac, Preview's Markup toolbar has a built-in signature tool (trackpad or camera). Open the PDF in Preview, click the Markup toolbar pen icon, then Signature. No third-party tool needed.
Converting PDFs to and from Other Formats
PDF to Word / Word to PDF
Microsoft Word (2013 and later) opens PDFs directly and exports to PDF from File > Export. Quality depends on the original PDF's structure — text-heavy PDFs convert cleanly; scanned images don't. LibreOffice (free, open source) does the same offline.
Images to PDF
On Windows, select multiple image files in File Explorer, right-click, and choose Print > Microsoft Print to PDF. This creates a multi-page PDF from your images with no additional software. On Mac, select images in Preview and choose File > Print, then "Save as PDF".
Quick Reference: Which Tool for Which Task
- Merge / Split / Reorder: PDF24 (desktop app, offline)
- Compress: ilovepdf.com or PDF24
- Fill forms: Browser built-in (try first), then PDF24
- Sign: Preview on Mac; DocHub or Smallpdf on Windows
- Convert to/from Word: Microsoft Word or LibreOffice (both offline)
- Batch / sensitive files: PDF24 desktop app or Ghostscript
For users who frequently work with PDFs, installing PDF24's free desktop app once covers 90% of tasks offline, with no file size limits, no watermarks, and no recurring cost.