Converting files to PDF: what carries over and what changes

Why convert to PDF at all

PDF solves a specific problem: fixed layout. Fonts, page breaks, images and page size stay put, the file opens in every browser and on every phone, and casual editing is harder than in the original format. Those strengths are also its costs. A PDF is awkward to edit and hard to turn back into an accurate Word or Excel file. So keep the original document as the version you edit, and use the PDF as the version you send, publish or archive. Converting also tends to flatten structure that only the original software understands, like formulas, animations and tracked changes. The guide to choosing formats explains when a PDF serves the reader best and when DOCX, XLSX, PNG or plain text is the better thing to send.

Office documents: Word, Excel, PowerPoint and OpenDocument

Word, Excel, PowerPoint, ODT, ODS, ODP and RTF files are converted by LibreOffice running on the server. The most common difference from the original is fonts. Common fonts like Arial and Times New Roman have look-alikes with the same letter widths. But fonts that only come with Microsoft Office may be swapped for similar ones. It can move a line or a page break. Spreadsheets follow their print settings, so set print areas and fit-to-width scaling before converting. Presentations lose animations and speaker notes, and hidden slides are skipped. OpenDocument files convert most faithfully of all, because LibreOffice reads them natively. Password-protected office files must be unlocked in their own application first.

Images and phone scans

Image converters embed each picture in the way that best preserves it. JPG photos are placed without recompression, so they stay identical to the originals. PNG, BMP and TIFF images are kept lossless, including every page of a multi-page TIFF. HEIC and WebP images are stored as high-quality JPEG because PDF can't hold those formats directly. Transparent areas are placed on white, phone orientation data is applied so photos appear upright, and SVG artwork stays vector. Pages are sized from each image at 150 pixels per inch. It can make camera photos into large pages that print correctly with fit to page. Any Image to PDF mixes formats, and Scan to PDF captures pages with a phone camera.

Text, Markdown and structured data

Plain and structured text is rendered as pages by the WeasyPrint layout engine. TXT to PDF keeps line breaks and alignment in a monospaced font on A4 pages, reading files as UTF-8. Markdown to PDF uses Pandoc to turn headings, lists, tables and code blocks into formatted output, falling back to plain text on servers without Pandoc. CSV to PDF detects comma, semicolon, tab and pipe separators, repeats the header row on every page, switches to landscape pages for wide tables and includes up to 5,000 rows. JSON and XML files are re-indented so their structure is readable. In every case values are shown exactly as written: nothing is calculated, rounded or reformatted.

Web pages, HTML, email and ebooks

HTML to PDF renders a saved HTML file with its print styles, while Web Page to PDF fetches a public page from its address. Neither runs JavaScript, so pages that build their content in the browser may come out incomplete, and pages behind logins capture the login screen. EML to PDF turns an exported email into a record with its subject, sender, recipient and date above the message. Remote images, including tracking pixels, are never loaded, and attachments aren't included. EPUB to PDF assembles a DRM-free ebook's chapters in reading order with the images packaged inside it. For files you can't identify, Universal File to PDF detects the format by extension and routes it to the right converter.

Safety built into conversion

Some source formats can carry active or remote content. An uploaded HTML page can contain scripts, an SVG can reference files on the server, an email can load tracking images and a web page can redirect to an internal address. The converters handle those files with care. Scripts are removed and never run. Links to other files or websites inside uploads are blocked. The web page converter refuses private and internal network addresses, even after a redirect. SVGs that point to outside files are rejected. Every upload is processed in a temporary folder that's deleted after the download finishes. The file security page describes these protections, and the PDF privacy guide covers what documents can reveal once they're shared.

After converting

A converted PDF is often the start of a workflow instead of the end. Check it first: page count, page breaks, fonts and anything that relied on external resources. Documents converted from several sources can be joined with Merge PDF and numbered with Add Page Numbers. Photo-heavy results benefit from Compress PDF, and image-based pages become searchable with OCR PDF. Records that must last should be converted to PDF/A with the archival tools. Each of these steps works on the PDF alone, so keep the original source files for any later edits.

Common workflows

Questions about converting files to PDF

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