A paper printout of a circuit board, at exactly life size, is one of the cheapest engineering tools there is. Place the real connector on the paper footprint and see whether the pins meet the pads. Drop the paper board into the enclosure and watch whether the mounting holes meet the standoffs. Lay the switches and display on the printout and judge the ergonomics with your hands, weeks before a fabricated board could tell you the same things. The whole value of the exercise depends on one word: exactly. This tutorial covers the reliable route — exporting from Gerbv to PDF and printing the PDF at true size — and the verification step that proves the scale before you trust the paper. Gerbv is on the download page with the Windows installation guide covering setup, the export itself follows exporting to PDF, PNG or SVG, and our Gerber viewer page places this trick in the full inspection workflow.
Why the route goes through PDF
Printers and their software love to help, and their favourite help is rescaling your page to fit their margins. The defence is to give the print path a format that carries an explicit physical size and a viewer that lets you demand it be honoured. That is why this workflow exports the layer view from Gerbv as a PDF, as described in the picture-export tutorial: PDF is a vector format in which the drawing has defined dimensions, and PDF readers offer a true-size printing choice — the setting is commonly labelled as actual size or 100% scale, as opposed to fit-to-page options that silently shrink the drawing by a few percent. Raster formats such as PNG can also be printed, but their physical size depends on DPI metadata being honoured end to end, which is one more assumption than the job needs. Vector PDF, printed at actual size, is the shortest path from Gerber geometry to trustworthy paper. Choose the layer stack for the check before exporting: for footprint and placement checks, top copper with silkscreen reads best; for enclosure checks, the outline layer plus mounting holes is the drawing that matters, cross-referenced with the DXF export if the enclosure work is happening in CAD.
The print settings that must not move
Three settings decide whether the paper is 1:1, and all three live in the print dialog rather than in Gerbv. First, scaling must be actual size / 100% — any “fit”, “shrink to printable area” or percentage other than 100 invalidates the sheet, however good it looks. Second, orientation and paper size must genuinely contain the board: if the board is larger than the printable area, the printer may clip or the software may offer to tile or shrink — shrink is the one answer you must refuse; print the board in sections for a partial check, or use a larger printer for a full one. Third, if your print path offers a choice between printing the document’s size and a paper size, choose the document — the exported PDF’s page is the size authority for this job. Consumer print paths default to making things fit pages; a fit check’s entire point is a page that refuses to flatter the board.
Verify the scale with a known dimension — every time
Never trust the settings; measure the paper. Pick a dimension you already know from the data: the board’s overall width is ideal, or a mounting-hole spacing you verified earlier using measurement in Gerbv. Measure that same feature on the printed sheet with a ruler — callipers are better — and compare. Agreement within ordinary paper-and-printer tolerance (a fraction of a millimetre over a board’s width) means the sheet is a fit-check instrument. A discrepancy with a clean signature — everything uniformly a few percent small — means a fit-to-page setting survived somewhere in the chain: find it, switch it to actual size, reprint, re-measure. A discrepancy in only one direction suggests the printer stretched the feed axis, which happens on some hardware; a second printer is the practical fix. This verification is not pedantry. It takes thirty seconds, and it is the difference between discovering a footprint error on paper and discovering it on a fabricated board with components already bought. Write the measured value on the sheet itself, with the board revision, so the paper’s credentials travel with it around the bench.
What to check on the verified sheet
With a proven 1:1 print, the checks are satisfyingly physical. Place the real connectors, switches, displays and any tall or odd components on their printed footprints: pin alignment, orientation, body overhang and finger access all become obvious. Check the board against its enclosure — holes over standoffs, edges inside walls, connectors centred in their cutouts — or, for a panel-mounted control, hold the sheet against the panel itself. Check human factors: labels readable in place, controls reachable, cables able to bend where they must. The same verified print is the natural companion to layer alignment checking: the paper proves physical fit, the stacked view proves the data.
The hobby context: toner transfer and etch-resist artwork
Home fabricators meet 1:1 printing from the other direction: for toner-transfer and resist-based home etching, the printed artwork is not a check but the manufacturing step itself, the pattern that will be transferred to copper-clad board. Everything in this tutorial applies with doubled force there — the scale verification against a known dimension is what stands between a usable transfer and a board whose IC footprints are uniformly a fraction off, which no amount of careful etching can rescue. Two cautions belong in that context. Orientation matters as much as scale: whether a given layer’s artwork must be mirrored depends on the transfer method and which side of the board is being made, so decide it deliberately for your process and verify the printed result against the design’s text and asymmetric features before transferring. And home printing resolution is the ceiling on fine detail: a verified-scale print can still be a poor transfer master for very fine traces, which is a printer limitation, not a Gerbv one.
Frequently asked questions
Why not print the PNG export instead?
PNG can work, but its printed size depends on DPI metadata being honoured through the whole print path. A vector PDF carries explicit dimensions and PDF readers offer an actual-size (100%) printing option, which makes true 1:1 output far more reliable.
How do I prove my printout is really 1:1?
Measure a known feature on the paper — the board width or a mounting-hole spacing you verified in Gerbv — with a ruler or callipers, and compare it with the data value. A uniform few-percent shortfall means a fit-to-page setting is still active somewhere; fix the setting and reprint.
The board is bigger than my printer’s page. What then?
Never accept the shrink-to-fit offer — that destroys the 1:1 property the check exists for. Print the critical sections at actual size for partial checks, or use a larger-format printer for a full-size sheet.